What do these weird icons next to my health and magic bars mean?

When grinding away in a dungeon as Louie in Recettear, I noticed that I have these weird icons next to my character picture:

But...I don't really get them. What are they supposed to indicate, and what sort of different icons are there in the game?

These icons are your special skills. Each adventurer has a selection of special skills they can perform using Button 2 (default X). You can switch through them using Button 3 (default C), the current skill being highlighted. These cost SP to do things more than a normal attack. And, just because, each skill is illustrated with a cute image of some girl that represents the attack.

You can view the skills of any particular adventurer in the pause menu by checking that adventurer's Status, and then hitting Button 1 (default Z). This will give you an overview of all of your adventurer's general capabilities and qualities, as well as their list of special skills in the bottom left. Each skill listed will explain what that skill does, as well as show the corresponding girl icon. The SP cost is not listed, however, so you'll have to figure that one out yourself.

Those are simply icons to let you know which of your adventurer's abilities you have currently selected. Each adventurer has their own cadre of ability icons. The faerie on the far left represents Louie's spin attack, while the faerie on the right represents his sonic boom.

The brightest icon (that is to say, the non-darkened one) is the current selected ability. Leveling up and adventuring with different partners will change the displayed icons accordingly.