very very briefly.
Ok, to supplement the nokia's "core" RAM/memory you can pause programs which are idle, and store them, and idle data on the flash card. when necessary, you laod the data back into core. this generates a lot of extra read and writes to the memory card which will wear it out faster.

since the card provided by nokia is too small for any real purpose, using as virtual memory and wearing it out quickly is its ideal fate.

"swappiness" is merely a way of telling linux kernel whether to try to keep things in core or to swap them out any time it feels like it.