Discrete vs on chip RAM for a mobility radeon 9000

Still in the hunt for a laptop and I found an ok mobile Athon system that advertised a mobility radeon 9000 with 64MB DDR VRAM. Now I noticed that it didn’t mention if it was shared with the system RAM (which is capped at 512MB for some reason). After doing some research, I found out there is discrete and on chip. Does discrete mean it’s not shared and on chip means it is? Thanks.

I’ve found laptop shopping to be much less straightforward than desktop shopping.