To add to your difficulties a little .... ;-}

There are at least six different types of concertina, all as different from one another as, say, a guitar from a mandolin.

There are, however, two main groups of free reed instruments (the official name for squeezeboxes) - most people get on better with one or the other, though some people happily play both.

Anglo concertinas, melodeons and (most) button accordions are called single action - they produce different (usually adjacent) notes of the scale on 'suck' and 'blow' - just like harmonicas. Most are restricted as to which keys they play in, but some are fully chromatic (these are the big, expensive ones).

Piano accordions, the big continental button accordions, and all the other types of concertina are double action - each button produces the same note on push and draw. These are almost always chromatic instruments, though they're usually easier to play in certain keys than others.

Which is best depends on you. But get the best you can possibly afford of whatever type you go for. Cheaper instruments are often actually harder to play, and less suitable for a beginner.

And remember - squeeze hard and squeeze often.

Andrew