> load averages:  1.65,  1.87,  1.49                                     11:29:17
> 32 processes:  1 running, 31 sleeping
> CPU states:  6.9% user,  2.5% nice, 37.9% system, 13.8% interrupt, 38.9% idle
> Memory: 8300K Act 7096K Inact 2488K Wired 11M Free 21M Swap 157M Swap free 
> 
> How do I interpret the fourth line of the top output?

      8300K Active	- pages in core, touched recently
      7096K Inact	- pages in core, valid, but not touched recently
      2488K Wired	- pages in core, not pageable
      11M Free		- unused page frames
      21M Swap		- swap space in use
      157M Swap free	- swap space free

> Does it state that my processes use 8300K of which 7096K is paged in
> and 2488K is paged out?

Nope.  

> I have 32MB (+ 2MB video RAM) physical memory. Is 21M unused?
> Why is there Inactive memory then?

It's an intermediate state between "active" and "paged out".

> Why can't I get the sum of the various memory types to add up to my
> physical memory size?

  8300+7096+2488+11*1024 = 29148

This is pretty close to 32meg.  I'm pretty sure that the space
actually occupied by the kernel's text/data/bss isn't counted here..

> And what is Wired Memory?

Memory which is protected against being paged out.. typically because
it's reserved for use for DMA, device drivers, etc.,

				      - Bill