/cl_maxpackets 100
/snaps 40
/rate 25000
/com_hunkmegs 512
i just want to know what these commands do and what are they useful for and should i use them? please explain each command correctly so i could understand 
Hunk megs sets how much of your ram the game will use, I have a basic idea of what the others are, but not enough to explain them.
/cl_maxpackets-maximum network packets /snaps 40- set the number of network snapshots per second /com_hunkmegs- defines how much memory the game can use for caching, by increasing this value, you can cake maps load faster, especially after you have played them once. Some maps also use shared components, then having these in memory decreases loading time. /rate-sets the maximum network rate, in bytes per second. snaps and maxpackets can be a set item in a server, these are cvar checks in the server. To see these, once you connect to a server, bring down the console and look thru the cvar check list for the appropiate item. Rate can be also, but usually if it above 4999, your alright. Hunkmegs depending on how much ram you have like I have a gig of ram, my hunkmegs is set to 300. /com_hunkmegs 300, it will take effect after restarting the game. Its not advisable to use more than half your ram. So it you have 512, use 256. Hope this helps
so you think i should use these settings if have 1mb internet connection and 1024mb and gf 6800 and amd 2800
Just try them, definately do the hunk megs, but increase it past 512 since you have a gig of ram.
/cl_timenudge -10 what that command do?
Timenudge was added in 1.5. Infinity Ward also inverted it. Use /cl_timenudge 10. As a simple explanation, it works like impact prediction in SoF2 and Half-Life basically making it so you don't need to lead your shots as much for the lag. Your hunkmegs setting should be half your installed memory. Regardless how much you have. Use these settings: /cl_maxpackets 40 /snaps 40 /rate 30000 /com_hunkmegs 512 /cl_timenudge 10 I'm just going to be nice and assume that you know what you're talking about and your connection is 1MBit up.