TLS is the most widely used protocol for securing TCP connections. We start with the history of TLS and an overview of its features. The core of the talk is devoted to describing how TLS provides two fundamental security properties: confidentiality and authentication. We discuss the use of X.509 certificates as well as the numerous ciphers and cryptographic algorithms TLS supports. Along the way, we see how TLS support in the Python standard library has improved dramatically in the last year and how to properly use it.