hi,
SP related to ANYTHING refers to Service Pack. Service Packs are addon programs that need to be applied to base softwares or apps to cover certain vulnerabilities or add extra features. For Tomcat, installing its SP would be very necessary as it is a web server and any loophole therein should be immediately fixed so that it is not exploited. Hence the Tomcat SP.

A good explanation

Hope this is what you were looking for.