The timeline on Trip captures all your activity on the site, recording your search terms and articles viewed. An extension of this is the 'star' feature. This allows you to highlight articles that you think are particularly 'notable'. To 'star' an article you simply press the star to the left of a particular result (remember you should be logged in). In the image below (click to enlarge) you can see the stars higlighted next to each article.
At any stage you can look back at your starred articles via a link at the top of the page called 'Starred items' (also highlighted).
You can also restrict any search you carry out to only show items you've starred. You do this via the 'Further refinements' section on the right-hand side of the results page (for interest, there is also the ability to restrict search results to those you've previously looked at).
I've also created a screencast for further information - click here to view.
NOTE: This is a slight expansion of an earlier post (from 2012) but it's an important feature we want to help users understand.