When giving a presentation, where is inside me appear to fly in and out or dissolved. What makes text in a presentation do this?

I think you can find the function from animations.

You can do this by using "Animation tab". Click on animation tab, where you can find list of "transition" for each slide. There will be default ready made transition available. If you move the mouse, you can feel the effect given by a particular model.

You can also set the sound and speed of the transition according to the need. You can also create your own animation by clicking on "custom animation". Each slide can have its own transition type, speed and sound.