There are 2 FollowCol Dashboard versions available - FollowCol Dashboard (SharePoint Tenant) and FollowCol Dashboard (SharePoint Site)
FollowCol Dashboard (SharePoint Tenant) is more powerful since it allows users to follow lists/columns from any site in your Office 365 tenant or SharePoint on-premises tenant (generally, web application). In addition, when deployed with Tenant-Scope by your tenant administrator, the app will save your FollowCols to a single location so no matter where you start the FollowCol Dashboard app you will have access to all the FollowCols you've saved from any site.
FollowCol Dashboard (SharePoint Tenant) must be installed by a tenant administrator.
For more information on Tenant Scoped Add-Ins/App see Tenancies and deployment scopes for SharePoint Add-ins
FollowCol Dashboard (SharePoint Site) allows site collection administrators to install and use FollowCol Dashboard on a site-by-site basis. You can create FollowCols from lists and columns in the current site collection and subsites.
FollowCol Dashboard (SharePoint Site) can be installed by Site Collection administrators.
Both FollowCol Dashboard versions function identically except for how far FollowCol Dashboard can "reach" to find SharePoint sites and their lists and libraries.
Users of FollowCol will only see a difference in how the Find List tab of Add FollowCol functions. For FollowCol Dashboard (SharePoint Tenant), "Search SharePoint Sites" will allow the user to find other sites within the tenant. For FollowCol Dashboard (SharePoint Site), "Search SharePoint Sites" will only allow the user to find subsites of the current site where FollowCol Dashboard is installed.
Both versions feature the ability for users to follow lists on FollowCol.com in addition to SharePoint.