Lock-up period

A lock-up period is a set timeframe after a company goes public when insiders—like founders, executives, and early investors—are legally prohibited from selling their shares. You'll see this mentioned in SEC filings (official documents companies file with regulators) around IPOs (initial public offerings, when a company first sells stock to the public). It matters because when the lock-up ends, these insiders can suddenly flood the market with shares, which often causes the stock price to drop. Think of it this way: if TechStartup Co. goes public and has a 180-day lock-up, the founders can't sell until day 181—but on day 182, watch out for potential selling pressure.