All of the four main genres (seinen, josei, shounen and shoujo) can be broken down into four basic categories.

The four types of Seinen:

1. Realistic stories handled in a mature way.
2. Look how much gore and violence I can fit in a chapter! Plot? What plot?
3. I'm a loser but I'm surrounded by a horde of hot women.
4. Moe.

The types of Josei:

1. Bunch of hot guys having adventures with homoerotic subtext.
2. I wonder if he's the right guy for me?
3. Family sitcoms.
4. Yaoi.

Types of shounen:

1. I'm trying to save the world.
2. I'm going to get stronger and beat you all!
3. I'm stupid and it's hilarious.
4. Boobs.

Types of shoujo:

1. I can't decide whether I like him or not.
2. I'm a magical girl and I save the world with sparkles!
3. I'm stupid and it's hilarious.
4. Bishies.