Equity is ownership in a company. Instead of paying employees entirely in cash, startups offer stock options (right to buy shares at a set price) or restricted stock units (RSUs, direct shares with vesting). Equity has three dimensions: grant size (percentage or number of shares), vesting schedule (when you earn it), and strike price (for options, the price you buy at). Negotiating equity well = building long-term wealth. A 1% grant at a $100M company valued at $10B could be worth $1M+. Poor negotiation = leaving millions on the table.