Sorry to ask a basic question here, but I couldn't find the answer by searching.  On the listing of weapons on this website, the polearms, as well as the lance (another polearm?), have the "control" property listed.  What exactly does this mean?  I imagine it is something along the lines of keeping an opponent at bay, but how does it work in the game?  Thanks in advance...

I think I figured it out, you are talking about the tags when you look at the weapon in the sidebar? like below:

Those don't have any mechanics behind them, they are just for sorting / filtering. The Control tags is referring to the Reach property that it has, in that it allows you to control battlefield movement more by threatening a larger area.

Also, the use of feats such as Sentinel and Pole Arm Master that lets you control your enemies movement.

I see!  Thank you both for the clarification :)