TLS was designed to operate on top of a reliable transport protocol such as TCP. However, it has also been adapted to run over UDP.
The TLS protocol was designed to provide 3 servers; authentication, encryption, and data integrity. Though, you are not required to use all three in every situation.
In order to establish a cryptographically secure data transfer channel, the peers must agree on a cypher suite and the keys used to encrypt the data. The TLS protocol defines a well-known handshake to perform this exchange, known as the TLS handshake.