Climbing is going up, or, depending on context, also down. It may refer to aircraft, a land vehicle, and humans and other animals. On land, in particular it refers to steep climbs, e.g. on a hill, mountain or stairs, in a pole or tree, etc. This article covers climbing without a vehicle.

Types of climbing
By terrain:

Rock climbing is climbing on steep rocky terrain. 
Mountaineering is climbing on mountains. 
Ice climbing is climbing on frozen water features. 
Mixed climbing is climbing on both frozen water features, as in ice climbing, as well as rocky terrain. 
Bouldering is solo climbing on boulders. 
Stack climbing is climbing sea stacks: near vertical columns of rock in the sea, near coasts. 
Buildering (pun on bouldering) is climbing on the outside of buildings. 
Indoor climbing is climbing on artificial climbing walls. 
Artificial climbing tower is a wooden or steel climbing wall used outdoors. 
Recreational tree climbing is climbing on trees. 
Professional tree climbing is climbing on trees for the purpose of hardware installation, pruning, or removal. 
By method of ascent:

In aid climbing, all means of ascent are used, from pulling on gear to climbing rope ladders attached to drilled bolts. 
In free climbing, climbers use only their hands, feet and other body parts to make progress. Ropes and other gear are only used for protection. 
By type of protection:

In traditional climbing (commonly referred to as "trad climbing") the leader places all protection. The climbing system is used to protect the climber against the consequences of a fall. 
Sport climbing is climbing on routes that are protected mostly or entirely by bolts drilled into the rock. 
Top-rope climbing uses a rope passed through an anchor at the top of the climb. 
Solo climbing is climbing without a partner. It can be done with a rope for protection ("roped solo") or without any form of protection at all ("free-soloing"). Deep-water soloing relies on water at the base of the climb to protect against injury. 
Bouldering relies on a partner (a "spotter") and a bouldering mat to avoid injury. 
Competitions
Competitions ("comps") are usually held indoors on purpose built climbing walls. There are three main categories.

Difficulty: competitors climb the same route one after the other. The winner is the one who reaches the highest point on the climb; if several competitors reach the top (or the same high point) the time taken may be used to determine the winner. Alternatively, some difficulty competitions involve a number of routes. Each route is assigned a point value based on difficulty. Competitors climb as many routes as they want, and their score is derived from their top few completed routes (with the exact number of routes differing between competitions). If a tie-breaker is needed, the numbers of "falls" (attempts) is counted. Some competitions limit the number of attempts, others do not. 
Speed: on two identical routes, competitors race each other to the top. The first to reach the top wins. 
Bouldering: Competitors work through a series of boulder problems on either a time limit, or an attempt limit for each problem. Points are awarded for completing each problem. In a tie-break situation or where limited attempts are allowed then points are awarded for the fewest number of attempts required to complete the problem. Bouldering competitions at higher levels usually have isolation to ensure that the competitors cannot see the problems before climbing them. 
Sometimes climbers must climb the route on sight. This means that they are not allowed to see other climbers on the route, or receive any form of advice (beta) from other climbers, and have only a limited amount of time to visually inspect the route from ground level. (Otherwise later climbers would be able to learn from previous competitors' mistakes, giving them a considerable advantage.)

In addition to competitions, festivals such as the Phoenix Boulder Blast and the International Climbing Festival (held in Lander, Wyoming) are a gathering place for rock climbers from around the world. They feature trade shows for climbing specific merchandise, clinics from world-renowned climbers, and parties.


Grading
Climbers grade the difficulty of the routes they climb. The grading system used varies from country to country (and region) and according to the style of climb. See also grade (bouldering). Grade opinions can vary from person to person. This phenomenon can be seen frequently in climbing gyms where grading will vary vastly between gyms.

Different forms of grading are also used for mountaineering and bouldering. There is no common bouldering grading technique yet.


Climbing techniques of animals
Many animals have developed excellent climbing techniques. Some animals, such as geckoes, can walk up and down vertical walls and even walk on ceilings without any problems. But some other animals have the same problem as humans in that climbing down is more difficult than climbing up, because backwards movements are required. The best known example are cats, which have to be rescued sometimes from trees, because they cannot climb down from them.


Climbing and the law
Rock climbing is not necessarily allowed on any given rock formation. The regulations vary from place to place but trespass laws are the most common impediment to climbing. Even where physical access is not an issue, climbing might not be allowed due to public liability concerns. Land owners often ban climbing during particular seasons to protect, for example, nesting birds. There are several organisations devoted to opening up new areas, or protecting access to existing areas, for rock climbing. In the USA, the largest of these is The Access Fund. In the UK, an equivalent organisation is the British Mountaineering Council's Access and Conservation Trust.

Climbing on buildings and structures ("buildering") without the owner's consent is illegal in most cases.


Climbing in popular culture
Climbing also has importance in some festivals. The best known festivals in which climbing plays an important role are technoparades, especially loveparade. In these parades, it is very common to climb on trees, street lamps, portable restrooms and other large objects. Climbing is also common during streetparade in Zurich and reincarnation in Hannover, although security staff and policemen pay close attention to climbers, since injuries and property damage have occurred in the past.

Rock climbing has been featured in many popular movies, such as Cliffhanger and Vertical Limit, but save for a few exceptions it is generally given an inaccurate portrayal by Hollywood and much of the popular media. The sport of rock climbing was swept up in the extreme sport craze in the late 1990s which led to images of rock climbers on everything from anti perspirant and United States Marine Corps commercials to college promotional materials.