Difficulty Levels

You've tried, and tried, but because The Computer Is a Cheating Bastard, you just can't win. But wait! You can just change the difficulty level, and now victory is assured!

Many strategy games, RPGs, and action games have difficulty levels. Often, you start the game at 'Normal', though sometimes at 'Easy', then work your way up. Most games with difficulty levels feature extra, even harder levels that you can unlock by beating the game. Some strategy games even let you change difficulty level between scenarios, letting you tackle a particularly challenging stretch without without being frustrated by Nintendo Hard difficulty.

There are two main kinds of AI and how the difficulty level interacts with them:

"Fun" AI: Used in asymmetrical gameplay where the player is fighting Mooks. Higher difficulties make them higher in number, and have more health. If the game goes beyond just Numerical Hard, they will generally fight more aggressively too. Outside of the AI, your character's health may be less, and obstacles such as bottomless pits may be re-arranged.
"Player" AI: Used in gameplay where each AI is treated as just another player, and ostensibly given equal footing with the real player(s). Higher difficulties make the AI smarter\faster\more skilled, and more often than not they'll cheat on higher difficulties, or cheat more than they do on the lower ones. There may also be harsher environmental forces that don't seem to affect the AI as much as humans.

In addition, many simulation and strategy games feature realism options that can be used to shut off certain complex features of the games, making them easier for newcomers to tackle.

An Omnipresent Trope in videogames. Many old school arcade games have difficulty levels which can only be set by the arcade's owner via DIP switches; these different settings are usually not visible to players, except in console ports that replicate some of them. Many arcade games allowed the player to influence one element of difficulty, the number of lives, by feeding extra credits.