How much RAM can my Macbook Pro hold MAX?

Can my Macbook Pro hold a MAX of 8GB or is it just 4GB? I'm getting different answers online and I'm a little annoyed at this point. My computer specs currently are:

15 inch Laptop
MacBook Pro 2.6 GHz Intel Core 2 Duo
2 GB 667 MHz DDR2 SDRAM.

Got my computer in 2009.

At Crucial.com it says it can hold up to 8GB when I select my computer processor speed from their list, but I noticed it saying DDR3 (and I don't know what that means to be honest). Here's the link:
http://www.crucial.com/store/mpartspecs.aspx?mtbpoid=7F3A5584A5CA7304
To the best of my knowledge I selected the correct computer, which I own, from their list.

Under "About This Mac", on my computer, it says DDR2 for the memory, on Crucial.com it says DDR3. As a result I'm confused and will that cause problems?

I'll be getting my RAM kit from Crucial.com, so do I buy the 4BG kit, because that's all my laptop can handle, or is it OK to get the 8GB kit, which says DDR3?

I do a lot of video and audio, so I would like to get my RAM up to 8 GB if it will.

Thanks