Grinding is a term used in video gaming to describe the process of engaging in repetitive and/or boring tasks not pertaining to the story line of the game. The most common usage is in the context of MMORPGs like Final Fantasy XI, World of Warcraft, Tibia, or Lineage  in which it is often necessary for a character to repeatedly kill AI-controlledmonsters, using basically the same strategy over again to advance their character level to be able to access newer content. MUDs, generally sharing much of the same gameplay as MMORPGs, encounter the same problem. Grinding may be required by some games to unlock additional features.
Synonyms for grinding include the figurative terms treadmilling (a comparison with exercise treadmills) and pushing the bar (it can be a reference to a weightlifter "pushing the bar" on a bench press, over and over to get muscle gains, or a reference to Skinner boxes in which animals, having learned that pushing a button will sometimes produce a treat, will devote time to pushing the bar over and over again, or also can be a graphical reference to push the character's experience bar to higher values). Related terms include farming (in which the repetition is undertaken in order to obtain items, relating the activity to tending a farm field), and catassing, which refers to extended or obsessive play sessions. Used as a noun, a grind (or treadmill) is a designed in-game aspect which requires the player to engage in grinding.
The most common form of level treadmill seen is the practice of killing monsters for experience points. In this way, the player progresses towards the next level to defeat more powerful monsters.
Grinding is a controversial subject among players. Many do not enjoy it, and disparage it as a symptom of poor or uninspired game design. Others embrace it, claiming that all games feature grinding to some extent, or claim to enjoy the practice of regular grinding. Some games allow players to bypass grinding by paying additional fees.
Why players grind
Several answers have been suggested for the question of why players grind. A major motivating factor is the players' desire to pursue what appears to be the game's ultimate goal, which for many games is to reach the highest level. There is usually little or no incentive for players to continually seek new challenges. Once they have found a means to reach their goal they will be averse to tackling new risks and instead repeatedly play through familiar content. Sometimes players might actually enjoy repetitive tasks as a way of relaxing, especially if performing the task has a persistent, positive result.
One reason that is less influenced by player choice is a lack of game content or to be able to battle stronger enemies. If the player experiences all interesting content at the current level before reaching the next objective, the only alternative might be for the player to grind to the next level. "Interesting content" is key here since the player might have been given "new content" that is too similar to previous content to be considered interesting by the player. [note 1]
Additionally, the players may grind for the enjoyment of being better at the game. Putting in the time to grind leads the player to gain experience and level up. Increases in level come with additional statistics boosts and abilities, which in turn allow the player to defeat stronger enemies. The gamer knows that time invested in grinding is directly related to strength or ability in the game. This relationship is encouraging to players, consistently rewarding their grinding effort.