The concept of survival in games usually refers to a lone person or a small group of people surviving against a formidable, and sometimes insurmountable, threat. There are two broad categories of survival games: "survival horror", which refers to games such as Silent Hill, and "survivalist", which do not have to be horror, and typically pit the player character against nature (and, frequently, other foes).
Survival horror games (SHG) have certain tropes that are worth discussing. First, SHGs typically limit the supplies you need to survive, whether that be weapons, ammunition, health, save points or light sources. This mechanic forces the player to be sparing with their use of these items, forcing tense decisions, and often leaving the player with no resources whatsoever. Second, SHGs usually feature supernatural enemies. A few examples of supernatural enemies are zombies (Resident Evil), ghosts (Fatal Frame) and monsters (Silent Hill). Lastly, SHGs frequently employ a less then ideal control scheme to make battling enemies more difficult and tense. For example, in many Resident Evil games, the player is unable to move and shoot simultaneously.
"Survivalist" games (sometimes, and perhaps more typically, referred to as "survival" games) do not have to employ horror elements.As opposed to SHGs, where the player's ultimate goal is, normally to, fulfill the requirements of the narrative, survivalist games have survival itself as their primary goal (though some games, such as The Long Dark, deviate from this model). Survivalist games distinguish themselves from SHGs by implementing various player states that affect your ability to survive. Examples of these are hunger, thirst, fatigue, core temperature (hypothermia or hyperthermia), sanity, disease and injury, many of which can only be overcome temporarily (for example, though you might eat some food, you will eventually become hungry again). The role of these various meters is, roughly, to simulate real-life survival experiences. To overcome these obstacles, the player must collect various items, such as food, clothing, water, medicine and light. Additionally, the player will often be tasked with crafting items, such as a bow and arrow for hunting, a shack for shelter, a fire for warmth and cooking or a splint for an injury. If this wasn't difficult enough, survivalist games may introduce enemies such as zombies, monsters or other human players (such as in Day Z). Unlike SHGs, survivalist games often give the player only one life (like a roguelike) after which the game must be restarted and items collected and crafted anew. Survivalist games also use procedural generation, open-world environments and sometimes have a strong focus on exploration.