Micro games are a concept that has fascinated me pretty much from the start of my interest in boardgames. Before I helped create a regular board gaming group, a lot of my gaming was done at restaurants or coffee shops or the like. Games that didn't take up much space and were easy to teach and quick to play for something that I was looking for.
And, quite frankly, something that has kept on being pretty darn handy.
The concept of micro games has been around since the 1970s, when pocket-size wargames started coming out with Ogre being the first and still one of the most famous. More recently, the tiny card game Love Letter has inspired a wave of little games aimed at hobby gamers.
Frankly, I'm not going to say that size or portability is the distinguishing feature of the micro game. a travel chess set is pretty darn portable but it is not a micro game. It is everything that a regular chess set is, just smaller. A regular deck of cards can fit in your pocket but I don't think anyone would consider that a micro game.
(Of course, I own a travel chess set and decks of regular playing cards and am glad of them. They just don't really fit into this particular discussion)
If you were to play a game of Ogre and a game of Love Letter back to back, they would be completely different experiences. The only thing that would be similar about the two games is that they would be fairly small. Ogre is a more complex game with more pieces and definitely takes longer to play. Since I've already ruled out size, what makes both of them definitively micro games?
This is what I think is the real defining aspect. They both have fewer pieces then you would expect. Ogre is an old-school wargame but it only has one small sheet of counters. Love Letter consists of just sixteen cards, plus some cubes for scoring. For their genres, they just don't have a lot of components.
And it really depends on the genre. You don't need anything to play charades and no one will be calling that a micro game.
Mind you, what is important is that micro games, as a concept, have been around since at least 1977. Probably longer but that's when the name got minted with Ogre. And, over the course of nearly four decades, a lot of micro games have been developed and made. And there are enough of them that are good, even great, to make them worth playing and enjoying.