Hidden Machine

A Hidden Machine or HM for short, is an item that, like a TM, is used to teach a Pokémon a move. HMs can be used an unlimited number of times and cannot be disposed of. Moves taught by HMs cannot normally be forgotten. These moves have a use as field moves in games in which they are HMs.

Moves taught by HMs are all field moves in the games in which they are HMs, but some field moves are not HM moves. Like all field moves, they can be used outside of battle even if the Pokémon has fainted or no PP in that move (using it in the field does not consume PP). Except for Generation V, specific Badges must be obtained by the player before they can use an HM move outside of battle to advance the game's storyline.

Ocarinas
There are certain items in the game, called ocarinas that serve the same purpose as the HM they are associated with. These items are kept in the bag and no Pokémon are required to use them, however they still follow the rules of Hidden Machines, such as badge requirements or locational restrictions.

List of Hidden Machines

 * HM01 (Cut)
 * HM02 (Fly)
 * HM03 (Surf)
 * HM04 (Strength)
 * HM05 (Flash/Defog/Waterfall)
 * HM06 (Rock Smash)
 * HM07 (Waterfall)
 * HM08 (Rock Climb/Dive)