Market capitalization, or market cap, is calculated by multiplying a coin's current price by its circulating supply. It is used as a rough way to compare the overall size of different cryptocurrencies, similar to how market cap is used to compare companies on the stock market.
A high price alone does not mean a coin is more valuable overall. A coin priced at one dollar with ten billion coins in circulation has a much larger market cap than a coin priced at one hundred dollars with only one million coins. This is why comparing raw prices between different coins is usually misleading.
Market cap is a useful starting point, but it has limits. It does not account for how easily a coin can actually be bought or sold without moving the price, which is a separate factor called liquidity.