The bid price is the highest price a buyer in the order book is offering right now. When you sell with a market order, your shares go to that buyer at the bid. The ask, or offer, is the seller side. On a liquid stock like SBI, bid and ask sit a few paise apart, for example ₹800.05 bid and ₹800.10 ask. On a small-cap with few traders, the bid might be ₹98 and the ask ₹101, and selling at market means accepting ₹98 even though the last trade printed at ₹101. Watching the bid tells you what your shares are really worth this second, not what the screen's last price says. If you want a specific price, place a limit sell above the bid and wait for a buyer to come to you.