Sockpuppet
A fake extra account a person uses to pretend to be someone else — to agree with themselves, evade a ban, manipulate votes, or create an appearance of support. The name comes from the hand puppet you talk through.
Uses: agreeing with/defending your main account in a discussion (making it look like more people support you), evading a ban (a "ban evasion" sockpuppet), manipulating votes, or writing fake reviews. When many sockpuppets act in coordination it becomes astroturfing (a fake grassroots movement) or a sockpuppet army. Platforms hunt them via IP, device fingerprinting, and behavior patterns, and ban whole clusters. Wikipedia has an entire investigation apparatus against sockpuppets. Related to bots (automated) but sockpuppets are controlled by a human. A fundamental form of identity deception online. Related to brigading and vote manipulation.