Cheating can be used for a number of effects, from bypassing a part of the game that is proving too difficult for a player, to accessing areas or items that would not normally be available (or at least not the character has reached a certain level or has amassed a certain amount of money). There are also cheats that, whilst may not make the game easier to play, enables the player to access interesting effects left in by the original developers.
Invulnerability
Also known as God Mode, this cheat creates a state in which the player character is invulnerable to damage. A variation of this cheat is known as Buddha Mode, where although the player character can get damaged or hurt, they cannot die (i.e. their health stops decreasing when it reaches 1).
Infinite Resources
One particularly popular cheat is the addition of an infinite amount of some resource such as money, ammunition or lives.
Invisibility
This chest mode causes the player character to become invisible to their enemies, so that they may not be targeted or attacked.
No-Clip Mode
This cheat disables the collision detection in the game, enabling the player character to pass through objects or walls. This can give players access to rooms or other areas that may not have been available to them, and may also enable them to avoid enemies or certain parts of the map. The no-clip mode may also be used for getting past a bug or glitch that would render the user unable to do anything except restart the game.
Flying Mode
Similar to the No-Clip Mode, the Flying Mode enables a player to move freely about in any direction, as if walking through air.
Items and Weapons
There are a number of ways that items or weapons may be added to a player's character without them having to buy or find them. The same principle is used to add money to the character's inventory, thus allowing them to buy anything that they find for sale.
Unlockable Items and Characters
Some cheats can unlock unused content or hidden items in the game that are normally only available to players who complete specific tasks in the game. For example, codes may be used to unlock new characters, pieces of equipment or special weapons.
Unusual Effects
Cheats may simply create interesting or unusual effects; for example, one cheat in Jurassic Park: Operation Genesis makes dinosaurs appear 'undead', whilst a controversial effect offered by such a cheat is the Hot Coffee mod for Grand Theft Auto: San Andreas, which turned the teen-rated game into an adults-only version.