We used to have a ? icon beside all of the items in the filters which redirected users to a link.
I’ve used my trackpad to draw a very, very poor version of what it used to look like 
The icons would only appear if there was a link defined here: https://github.com/focallocal/fl-maps/blob/master/imports/both/i18n/en/phm/categories.json
Please find, or recreate it and then tag me so i can update the links