TLS and SSL are effectively the same thing, but just different versions of each other where TLS is newer than SSL. More often than not people are actually referring to TLS.
In the scope of SQL Server, TLS is enabled via SChannel which is a/the Windows secure channel implementation. This is the same system used by HTTPS on Windows. It's enabled by default on Windows, but depending on what versions of everything are in play you would need to futz with some registry settings to enable things:
Server options with flags
Enabled. This KB goes into detail about enabling TLS 1.2 on the servers.
Which version of TLS you're using is dependent on a number of factors such as OS, server, and client versions. For instance SQL 2005 doesn't support TLS 1.2, and anything newer requires explicit configuration before it'll be activated. See the above-mentioned link for specifics.
I'm not aware of a way to extract the exact version used via API or configuration. You may have to check the TLS handshake via wireshark or similar.