@javalps the boost button is similar to the "retweet" option on Twitter which pushes the post onto your page to your followers so they can see it as well. Favorites and bookmarks do not do that.
I use the favorite button to basically say "I see you" or "this was not ignored". I basically do not use the bookmark button.
The boost button I use for things that I think other people should see, even my own replies cause replies aren't shown to your followers unless they also follow the person you're replying to. So if I think my reply to someone is useful information for others, I'll boost it.
I'll probably boost this reply here as well.