Land uses are defined by each jurisdiction's municipal code. They are a list of uses that exist in your community, and can be things like: barbershop, light manufacturing, restaurant, or single-family dwelling. OpenCounter takes the list of uses from the muni code, categorizes them, and maps them. All of your jurisdiction's land uses can be found on the land uses tab in OpenCounter:Zoning, as shown below.
From this screen, you can see a summary of clearances: the green box reflects the number of zones where this use is permitted, yellow where this use is conditional, and red the number of zones where this use is not permitted. The action icons on the right (circled in green above) lets you do 3 primary things:
List icon: See/edit permissions for this use across all zones.
Pencil: Edit the use name, the definition, add keywords, and set it as a featured use.
X: Delete the use.
Above those icons, you also have the option to add a new use code by selecting the + sign.