When to use the favourite button on Twiiter ?

[Stay+ve]

I notice people use it on every reply they're getting, and every tweet they like.
So is it exactly similar to the "Like" button on Facebook ? If so , why is there a favourite list in your profile. What's the point to have silly replies and random tweets saved for you to read ?

In other words, should the favourite button used for very interesting tweets that caught your attention and want to remember later ?

[Daniel]

Use it If There is a Tweet That you Really Like That you Think is your Favorite Tweet of There's