各自 (gè zì) means 'each (of two or more parties) respectively' — it stresses that each individual in a group does something separately, often with their own thing. Unlike 每 (měi, 'every'), a general quantifier, or 各 (gè), used before nouns or verbs, 各自 is a pronoun that stands alone and emphasizes separate, respective actions. 各个 (gè gè) focuses on 'every single one' rather than separateness.