Your main RAM is not the same as video RAM. Video RAM is how much memory allocation you have in your graphics card. They sometimes refer to video ram as "VRAM." The amount of vram can vary from card to card. Most GPU's vary from 512MB RAM, all the way up to 6GB RAM.
But yes, to answer your question, they are not the same. Sometimes your main RAM can help pick up the slack for multiply tasks, but that usually only works for video editing or photo processing. Having a good amount of VRAM in your GPU is where it will count most, because graphics rendering is processed on the GPU. Generally, 2GB's or ram is the standard to have in a graphics card nowadays.