Filters on a walkaround lens

[knightrider]

I'm looking at filters to keep on my general-purpose lens, which will be on the camera most of the time.

I freely admit I know very little about filters - the difference between UV and skylight, polarising and circular polarising, the list goes on lol...

Is it generally a bad idea to keep filters on all the time, instead using them only when necessary?

I have no specific effect in mind, all I'd like is some sort of polarising to help with outdoor shots, as well as some lens protection...