MAME is effectively the motherload of all emulators that is geared to run games & software for the various platforms it supports as accurately as possible, once they get stuff to a working state.
MAME was originally known as the Multiple Arcade Machine Emulator & was geared to handle only coin-op arcade games. HOWEVER, around version 0.162 (released May 27, 2015), it's sister emulator MESS (Multi-Emulator Super Station) was merged into MAME to effectively make it the "Multiple All-purpose Machine Emulator" (this is not an official name, but better reflects the emulator's capabilities). MAME was designed to be a functional archival tool for games, considering that the video game industry has fairly poor record of preserving itself (as companies have lost their own source code to some of their games)... even though it treads into legally questionable territory. HOWEVER, since MAME doesn't attempt to add any games that are less than 3 years old (although it can take multiple years to get to a somewhat working state).
Since MAME is geared more towards execution accuracy of the software, the system requirements can vary greatly depending on the game you're trying to run. For many classic arcade games released before 1990's will have very low requirements that most modern systems (generally, if you've hit the recommended specs for the OS, you should be OK). However, the more complex the game (& the original hardware), the higher the system requirements will become.
Hope this sheds some light on the subject.