Explaination of the meaning of "Trigger Jobs"

Can someone explain this to me?

With my reading on the Sig P226, it seems people feel that the trigger on the is a little to much lbs. ft. needed to activate it on the first pull since it's SA on subsequent shots.

So they recommend a trigger job to lighten it up. What's the process of this, do you replace the trigger, or do you take it to a smith to work it down to where you want it? Both?

I'm just a little confused, thx.