Collection pages include useful statistics which can help users understand how popular a collection is or allow a curator to see how well recieved their content is. Users who have downloaded a collection can endorse it or leave an up or down vote on the success rating.
Curators can view their success ratings on their collection page, on the right panel. This area will show revision specific, last 30 days and all time success ratings. Note that if a collection hits above 75% success rating, the color will be green and the collection will also receive the "easy install" tag when either the revision or last 30 day rating hits at least 75% success rating.

This is a measure of users who have downloaded the collection and rated if the collection worked on in their setup. It is intended as a measure of "does this actually function?", rather than if the user has a high opinion of the overall themes.
Success ratings are also tied to a specific revision of the collection. If you couldn't get revision 1 to work and gave it a downvote, you can still upvote revision 2 independent of that. Revisions require at least 3 ratings to show a percentage. Users are encouraged to leave a rating on any collections they install to help others understand if the list creates a functional installation or not.
To ensure that the user has actually had the opportunity to play the collection, they may not leave a rating until at least 12 hours have passed since the initial download.
Users can vote a collection in 2 ways. By going into Vortex->Collections and viewing your collection, or with the automated notification they receive after they install a collection & 12 hours has passed.

Success ratings are no longer public on the collection page, but it is still possible to view a collection's specific revision's success rating by adding that collection to Vortex. It will be visible under Vortex->Collections after you view the collection in question as shown above.
Collection users are able to sort collections by success ratings as well, though this is not always an healthy way to sort the collections as a collection with just 3 votes can have a 100% success rating and the number could eventually go down whereas a collection with 300000 votes won't be able to hit 100% success rating that easily.
An endorsement is tied to the entire collection. Endorsing a collection is to show appreciation of the collection as a whole. Was it fun to play? Did it have enjoyable themes? Are you extra thankful for the efforts of the mod authors and curator who made it possible? That's an endorsement. An endorsement to a collection will not however translate to an endorsement to every single mod on the collection one by one separately. You need to endorse these mods yourself to increase the endorsement count of the mods individually.
Endorsements can only be given 12 hours after the initial download of the collection.
Collection endorsement and download statistics will be open to public and users can sort collections using this statistics, so it is always important to pay attention to these statistics when you can. By default, collection pages are sorted by endorsement counts.

Each time a user adds a collection to Vortex the download counter will be increased by 1. This does not represent successful installs as the user could have aborted the installation before it completes. It is possible to view the unique and total download numbers if you open a collection page and hover your mouse over to the download number.
