Milestones are a type of Task that have an added level of significance. Milestones can only last one day in duration and, as such, are used to denote key days in your Project/Event's progress.
Being late on Milestones generally has wider implications on the progress of your project delivery, so WeTrack displays the date of your milestones in bronze, silver or gold colour according to its status. Milestones too, like any Tasks, are given a RAG status according to their progress.
We recommend checking out this article on the difference between tasks & milestones, and how to use them together.
NOTE: Milestone Tasks are denoted on a Gantt Chart by a diamond shape, rather than the usual square/rectangle. See the below image for an example. We recommend reading this article on using Gantt to track your milestones.