Maneuvers and stances belong to one of nine disciplines. Each discipline has a key concept, weapons associated with it, and a skill associated with it. I tend to think of the guys from ToB as a kind of "spellcaster" as far as learning the system goes. Readied maneuvers are equivalent to prepared spells. Initiator level is the equivalent to caster level.
Maneuvers: Think of these as spells for melee guys. They break down into three categories:
Strikes: These are single melee attacks as standard actions which general have some extra bonus thrown on there, such as some extra damage dice, or a fancy flip-over-bad-guy and attack him kind of thing.
Boosts: These are swift actions to activate and provide some benefit for the round. For example, burning blade (Desert Wind 1) gives an extra 1d6+X fire damage on your attacks for that round.
Counters: These are, as they sound, abilities you activate in response to being attacked. Some negate attacks, some allow for retribution, some give a bonus to saving throws.
Stances: You know many fewer stances than you will ever know maneuvers. You gain the benefit of the stance all the time (it is not an action to use them). An example stance is child of shadow (Shadowhand 1) which grants concealment to your character if you are in shadows.
The way the system is set up you have to take lower level maneuvers to meet the requirements for higher level maneuvers within a single school. Maneuvers are more generally limited by level at the same progression as wizards (2nd level maneuvers at 3rd level, 3rd level maneuvers at 5th level, etc).
Well, getting into the class requires a small number of maneuvers which would require you to take a level of swordsage or a couple feats. Monks are lacking feats so I assume you'd be going with the level of sword sage. A level of swordsage would grant 6 maneuvers and a stance. This would mean you'd get to select 6 maneuvers. Of these 6 maneuvers you would declare 4 of them as readied. Only readied maneuvers can be used, but changing your readied maneuvers only takes 5 minutes so its changeable outside of combat. Once a maneuver has been used you have to take a full round action to recover the maneuver to able to use it again.
Assuming you already have a couple monk levels and you are adding sword sage on top you have the possibility of gaining higher than first level maneuvers (See page 39 about Initiator level). For instance, as a Monk 4 Swordsage 1 you'd have an initiator level of 3, and be able to pick up 2nd level maneuvers assuming you met the other requirements for those.
