Social epistemology studies knowledge in social contexts. Knowledge is 'social' when its holder communicates with or learns from others (Epistemology in groups), or when its holder is a group as a whole, literally or metaphorically (Epistemology of groups). Group knowledge can emerge explicitly, through aggregation procedures like voting, or implicitly, through institutions like deliberation or prediction markets. In the truth-tracking paradigm, group beliefs aim at truth, and group decisions at 'correctness', in virtue of external facts that are empirical or normative, real or constructed, universal or relativistic, etc. Procedures and institutions are evaluated by epistemic performance: Are they truth-conducive? Do groups become 'wiser' than their members? We review several procedures and institutions, discussing epistemic successes and failures. Jury theorems provide formal arguments for epistemic success. Some jury theorems misleadingly conclude that 'huge groups are infallible', an artifact of inappropriate premises. Others have defensible premises, and still conclude that groups outperform individuals, without being infallible.