A Service record (SRV record) is a specification of data in the Domain Name System defining the location, i.e. the hostname and port number, of servers for specified services.
Basically, with the current A record system of directing domains, if you want play.mcservernamehere.com you will HAVE to have the server to be on the default port (25565). Otherwise, you will have to go to play.mcservernamehere.com:20202 if your MC port was 20202.
With SVR lookup, you can direct your domain to your particular server port without the need for the :20202 port. And it saves on precious, precious IP addresses.
tl:dr; it works and looks much better than the current A-record implementation.