The "loop point" is a way to designate when the buttons will appear. See "Set the Menu Loop Point" here:
You don't have to use After Effects, but I think these help files are more useful.
So, there is also a way to use After Effects for buttons? Well, when I opened the After Effects using the encore....everything what I had in Encore was also in After Effects. However, when I added some effect to the object (in encore it is a button), in encore it didnt change anything. Are there any importnant things what i should do? Thank you!
I often do similar with just PrPro and Encore. I create a Video from the PSD, but without the Buttons visible, and "animate" it with a Dip-to-Black, to fade in the Menu (you can easily have a Video playing, basically as a PiP (Picture in Picture). I might then animate the "appearance" of the Buttons, say having them fly onto the Menu from off-screen. Note: at that point, they are not REAL Buttons, but just animated graphic elements. As soon as they hit their position, that "intro" Video (set to Play First in Encore) ends, and then links to the real Menu.
In AE, you can have real Buttons animated in.