What does a startup accelerator do?

An accelerator is a fixed-term, cohort-based program that invests a standard amount on standard terms in exchange for equity, and surrounds companies with advice, peers, and a demo-day introduction to investors. Y Combinator and Techstars defined the model.

The standardized deal is the signature: every company in a batch gets the same terms, published in advance. The durable value is usually network and alumni effects more than the capital itself.