An evolution chain shows how a species progresses from one form to another. Some chains are linear, while others branch into multiple possible evolutions based on items, friendship, gender, location, moves, time, or other conditions. Branching evolutions let the same basic species fill different roles and may have different types, stats, and movepools. Before choosing a branch, compare its availability and intended role in your game. Some evolution choices are difficult to reverse without catching another base Pokémon, so it is sensible to save or research first. A chain can also include baby Pokémon obtained through breeding in certain generations.