What is the main difference between TCP and UDP?

The main difference between TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) is rooted in how they handle data transmission. TCP is designed to ensure reliable communication; it establishes a connection before data transfer, guarantees that packets arrive at their destination in the correct order, and provides error-checking and retransmission of lost packets. This process makes TCP slower than UDP, but it is more reliable for applications where data integrity is critical, such as web browsing, file transfers, and email.

In contrast, UDP is much faster because it sends packets without establishing a connection and does not require acknowledgment of receipt. This makes it suitable for applications where speed is more critical than reliability, such as video streaming, online gaming, or voice calls, where some data loss is acceptable.

Given this understanding, the selection of TCP as slower but more reliable and UDP as faster but less reliable accurately captures the essence of their operational characteristics.