Integrated cards such as the Intel HD or GMA series aren't that good for gaming. Usually, those cards take up to 1792 MB of RAM from the laptop's memory.
A dedicated card has its own amount of RAM that it draws from, and some discrete cards can pull from the laptop's RAM if it requires more memory.
If you're looking to purchase a new laptop and want enough RAM, 4 GB should be plenty for most applications and games.