Internal Memory (SDcard?) VS. External SDcard

[bradleonard]

I am having a hard time understanding the purpose of the internal SD card memory and how it relates to external memory. It appears to me that that when I browse these storage mediums with either Astro or when I mount them on the computer, my files are almost duplicated on each card.

Can someone explain why these two different flash memories would have identical or nearly identical content? Maybe it is something that i messed up when reformatted my card and swapped out the 8gb for a 16gb.