What are micro-cap cryptocurrencies?

Could you elaborate on the concept of micro-cap cryptocurrencies? I've heard the term but am unclear on the specifics. Are they cryptocurrencies with a relatively small market capitalization? If so, what range does the market capitalization typically fall within for these types of cryptos? Also, are there any specific characteristics that distinguish micro-cap cryptos from larger, more established cryptocurrencies? Furthermore, what opportunities or risks might investors encounter when considering micro-cap cryptos for their portfolios? I'd appreciate any insights you could provide.