Market cap
In short Market cap is a token's price multiplied by its circulating supply, a quick measure of relative size that says little about real liquidity.
Market cap, short for market capitalization, is the total value the market assigns to a token. You get it by multiplying the current price by the circulating supply. It exists because price alone tells you nothing about size: a token at $0.001 can be far larger than one at $50, depending on how many units exist.
Mechanically, the number is simple. Take the last traded price and multiply it by every token that is actually in circulation, which excludes tokens that are locked, unvested, or burned. Nobody paid that total, though. It only projects the price of the latest trades onto the whole supply, so a single small buy can move it a lot. Data sites pull supply figures from the team or from on-chain data, which is why the same token can show different market caps on different sites.
For a buyer, market cap is a rough yardstick of how much room a token has to grow and how much risk it carries. Going from a $1M market cap to $100M needs a 100x, while going from $10B to $100B needs a 10x, and the second is usually harder. Small caps also tend to have thin liquidity, so they swing hard and are easy to push around.
The main trap is treating market cap as money that could be taken out. A token with a $5M market cap and $20k in its liquidity pool cannot be sold at that valuation, because selling a few thousand dollars' worth would crash the price. Another trap is a small circulating supply with a huge locked portion. The market cap looks tiny until unlocks arrive, so compare it with fully diluted valuation and check the vesting schedule.
Before trusting the figure, check the supply on a block explorer, look at how much liquidity sits behind the price, and see how concentrated the holders are. If a few wallets own most of the supply, the market cap is mostly a number those wallets control.