請哪位解釋一下TOP命令中各項顯示是代表什麼.

toad_ora

top - 19:57:49 up 30 days, 23:41,  2 users,  load average: 3.13, 3.73, 4.80
Tasks: 290 total,   2 running, 288 sleeping,   0 stopped,   0 zombie
Cpu(s): 21.3% us,  2.2% sy,  0.0% ni, 72.8% id,  3.4% wa,  0.0% hi,  0.3% si
Mem:   5971492k total,  5959892k used,    11600k free,    20840k buffers
Swap:  4198312k total,    20368k used,  4177944k free,  5001624k cached
中的如下項,:請幫忙解釋一下:
load average: 3.13, 3.73, 4.80
Cpu(s): 21.3% us,  2.2% sy,  0.0% ni, 72.8% id,  3.4% wa,  0.0% hi,  0.3% si

toad_ora

PR , NI , VIRT , RES , SHR ,S , 還有分別這幾項又是代表什麼意思