Ingame window

1- Resources (Minerals, Vespene, Honor Tokens)
You will receive minerals and vespene for every single kill and everytime you finish one quest. Honor Tokens are rewarded when you take out the last boss of each race (Protoss, Terran, Zerg)

2- Inventory Slots (1,2,3 on numpad or F5,F6,F7)
The first slot (F5) its the current equiped gear, the other two slots (F6 and F7) are the inventory.

3- Skills upgrade. Press Q to open the skill updaring window. You receive one skill point every level up, so don't forget to use them.

4- Skills. After you upgrade them, you will unlock the skills (B one is there by default and cannot be upgraded further).

5- EXP bar. Each kill will fill it up, when its maxed you will level up receiving extra stats (every 5 levels) and receiving one skill point. (NOTE: has you can see level 30 it's cap)

6- Stats. Each stats increases certain stuff, like damage, hp and mana.

7- Character info. Here you find the damage you do, the defense, HP and mana of your character. You can raise these by equipping better gear or leveling up.

8- Buffs. They're not exactly buffs, but i couldn't find a better way to describe this. They're the pictures of some of your equipments. Not sure if Dem had any specific idea for this, but atm, they don't do nothing special.