There are many different types of pets in Battle Run, here are the list of them all.
Attack pets are pets that are mainly made for killing, they aren't that fast but do a lot of damage when killing a player. These pets are mainly use to build up one's K/D Ratio.
Ex: Robo Spacecraft
Speed pets are pets that are mainly made for speed and stamina and sometimes come with an attack but not all the time. These pets are mainly used in competitive play.
Melee pets are pets that have a persistent attack and speed. They may not have the damage of an attack pet or the speed or stamina of a speed pet, but they are great for competitive play and building up your K/D Ratio as well. Most pets fall under the Melee category.
Dropped pets are pets that drop an obstacle to slow down players behind them. They are good pets if ur first but they are very terrible attack pets. They are used mostly in casual play because they can secure a good lead.