Three main types of computer networks are described:
1. Local Area Network (LAN) covers a small physical space like a home, school, or single building and has the fastest speeds.
2. Metropolitan Area Network (MAN) connects multiple LANs within a larger area like a city and has faster speeds than WAN but slower than LAN.
3. Wide Area Network (WAN) is the largest type of network, connecting LANs and MANs over long distances like countries and continents, and has the slowest speeds of the three types.