ADCollector is a lightweight tool that enumerates the Active Directory environment to identify possible attack vectors. It will give you a basic understanding of the configuration/deployment of the environment as a starting point.
ADCollector is not an alternative to the powerful PowerView, it just automates enumeration to quickly identify juicy information without thinking too much at the early Recon stage. Functions implemented in ADCollector are ideal for enumeration in a large Enterprise environment with lots of users/computers, without generating lots of traffic and taking a large amount of time. It only focuses on extracting useful attributes/properties/ACLs from the most valuable targets instead of enumerating all available attributes from all the user/computer objects in the domain. You will definitely need PowerView to do more detailed enumeration later.