What is it
Why it's on hold
Moment is not developed anymore. Basically the only reason for using Moment would be if you can'f find an alternative that supports Internet Explorer 8 or if you require a library that only supports Moment.
In short, there should be a really good reason if Moment should be used.
If you need to work with dates and times, consider using Luxon instead.
How to learn it
Install instructions can be found here.