Battle Dudes is a 6-button game. This means that you have 6 different buttons, correlating to 6 different types of attacks. They are labeled as:
LP- Light Punch
MP - Medium Punch
HP - Heavy Punch
LK - Light Kick
MK - Medium Kick
HK - Heavy Kick
These are your attack buttons, also known as normals. Each one correlates to a different attack, with lights being quick but weak attacks, and heavies being slow but powerful attacks, with mediums lying in between. These make up the core of the gameplay of Battle Dudes. These vary a lot between characters, so experiment a lot with your character of choice and get a feel for how you're supposed to use your normal attacks.
You also have 4 other buttons that are not directly related to your attacks. These are:
FT - Forward-Tag
BT - Back-Tag
S - Start
M - Menu
Your FT and BT buttons are not used anywhere except in the Tag Team game mode, which you can read more about in the features submenu in the navigation bar. It is also used in some other non-game actions. Your start button is used for taunts, and other various non-game actions. Generally this will never be used as an actual attack. The menu button simply opens the pause menu, and also is used for other non-game actions. This button, like start, is never used for attacks or other significant actions in game.