Here is how its used:
The Technical Machine, or TM, is a small disc insulated with wax to protect it from the sorts of elements pokémon trainers wind up in. Each one is written with everything you need to know about the move correlated to it's number. There is a disc drive on the pokédex that TMs are designed to be inserted into. Tutoring instructions for trainers are the main part of the TM disc.
There are different instructions for different pokémon, and a lot of other useful data. Using the disc as a guide a trainer can generally teach one pokémon the move in one to three weeks. This is perfect, because that is about as long as the disc can be used. After a few weeks of usage, enough time for one teaching, but not enough for two, the wax causes the disc to crack and become unusable.
HM discs are made with a different kind of protective coating, allowing it to be used indefinitely. This special material is incredibly expensive, making it unwieldy for the manufacture of many copies. The Hidden Machines and called so because of their rarity. Occasionally Hidden Technical Machines are created, usually on commission, the data from a standard TM imprinted on a HM disc.
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In the forum mechanics side of this allow some time, usually a few weeks (IC if possible), from when your pokémon begins learning the TM to when you can use it in battle. The time is considerably less if the move is of the same type as your pokémon (Normal doesn't count). When you begin teaching it, designate the move it is overwriting. During the teaching that move can be used, but it sets the lessons back a few days. The TM is beyond use by the time you finish and must be replaced before repeating.
