Your troops, or units, are your attacking method. You have your troops and your enemies do as well. When you attack an enemy's headquarters, your troops can be attacked by Simple Turret, units, and Sniper Turret.
A defensive base does not have any units except for the Commander. It has a mix of Simple Turret and Sniper Turret. These bases have more protection, and can really damage your units. In a defensive base, it is hard to break through their defenses. You want to use a tank, one of your units, with full upgrades, using the Armory, and position a few near one wall. The tanks that have the cannon upgrade can shoot and break the walls without the turrets noticing. Sometimes the defensive base can shoot your tanks even though they have the invisibility upgrade.
A hybrid base has units and the Commander. This base also has a mix of Simple Turret and Sniper Turret. This base type has less protection, but more units than the defensive base. This base can protect and damage your troops before they get to the target location. This base can also fight back, which means you need to be very careful. You can use any units you choose.
An attacking base is only units and Commander. There are almost no turrets and defenses besides walls unless they put turrets behind their barracks. They contain mostly houses and sometimes generators. They can usually hold about 75-150 unit space or about 50-75 units. You can attack the base using any troops after you get the wall down. It is a bad idea to attack the base with only a few units.