Short answer
Volume is the total value traded over a period, often 24 hours. It shows how active a token is, but it can be inflated by bots trading with themselves.
High volume usually means lots of people are buying and selling, which tends to come with tighter prices and easier exits. Falling volume often means attention is leaving.
Volume is easy to fake, though. A single actor can trade back and forth between their own wallets to make a token look busy. Signs of this include huge volume with very few unique traders, or volume many times larger than the liquidity pool.
Treat volume as a hint, not proof, and check it against the number of holders, the trade history and the liquidity.
See the checks for yourself
18+ only. Self-custodial: you keep your keys. 0.5% per trade, no minimum. Memecoins can go to zero.