Welcome to the forum.
As for Rendering, are you referring to the process of producing files to give you the smoothest playback, by hitting the Enter/Return key?
If so, and you do not have a yellowish-orange line ABOVE the Clips, then there is no need to Render, as there is nothing to Render. That keystroke would result in playback.
For more info on Rendering, see this Tips & Tricks article: http://forums.adobe.com/message/4068277#4068277
Thank you Hunt,
yes, I do have a yellowish-orange line above the clips, and the unrendered clips are in a very bad quality. Every time when i put the marks above the clip and press the Enter/Return key the Renderering-window appears for a second, then it disappears and the clip starts to play unrendered. Might there a be any basic setting fpr the rendering?
This yellow orange line indicates a mismatch between your project settings and your video specs.
What model of camcorder is your video coming from and what format and resolution is it?
What are your Project Settings, as listed under the Edit menu?