Since 2005, Y Combinator has invested in nearly 3,000 companies, including well-known names like Airbnb, DoorDash, and Stripe, with a combined valuation of over $300B. They offer programs such as Startup School, YC batch program, Work at a Startup, YC Series A, YC Growth Program, and YC Continuity to help founders at different stages of their startup journey. Y Combinator's unique model involves investing a small amount of money in a large number of startups and working intensively with them for three months to refine their pitch and prepare them for Demo Day.