I hope that I'm writing in a right section. I have a videocamera full HD (low price) and a SD class 2. Can this type of class film HD videos or it will save bad quality videos?
According to the SD association, Class 2 SD cards have a minimum writing speed of 2 MB/S. That is not sufficient for HD recording, let alone Full HD. Even though that is only the minimum speed, I don't think the SD card will be nearly good enough. If you already have the camera and the SD card though, why not try it out for yourself? Worst thing that can happen is the camera won't record anything or stop after a few seconds.
Here's an overview of the different speed classes. Depending on your camera model, I would recommend you get a class 6 or 10 SD card. The manual of your camera should also state which SD writing speed is required to record Full HD video. Most cameras (at least in the medium to high pricing range) will also allow you to change the (average) bitrate video is recorded at, you should also look into that. Use that information to decide on an optimal SD card for your needs.