It explicitly enables TLS 1.0, 1.1 and 1.2, and disables some obsolete security protocols, as well as TLS 1.3 (normally a bad idea, but Microsoft's implementation of it has known bugs).
Without applying those registry values, uTorrent will default to TLS 1.0 for HTTPS connections, which is deprecated and therefore not supported by many trackers. They affect anything that relies on the SChannel API, but have no effect on programs that use their own TLS stack (e.g. Chrome, Firefox, Java).