Hi Sue
In Learn some activities such as forums and databases have a rating available for each user. Custom scales could be created for the stars The ratings go into the gradebook for the course and could be have grade calculation to average the ratings for all users. Displaying the rating in the course catalog may require some custom work though.
If you are using Engage then there is a Like option for resources with the total likes able to be displayed on the content. It is also possible to rate a playlist this playlist would show in the catalogue but not the rating. There are some some engagement reports such as Playlist engagement that includes the Rating field but this is at the user level and doesn't look as though it can be aggregated .
At the complex end of the scale - the recommendations engine can be set up to recommend content based on interactions with the content from similar people in the Recommended for you block
There may be some third party plugins or other workarounds that Partners have that may help achieve this.
regards