Market cap, short for market capitalization, is a measure of the total value of all coins of a particular cryptocurrency that are in circulation. It's calculated by multiplying the current price of the coin by the total number of coins in circulation. Crypto sector market caps refer to the combined market cap of all cryptocurrencies in a particular sector. This can provide insight into the size and significance of that sector in the overall cryptocurrency market. However, market cap should not be the only factor considered when assessing the value or potential of a cryptocurrency or sector.