Windows 7: What's free space consolidation?

hello, thanks for reading!

there is an option in command line promt:
which will consolidate free space, it takes about 40 or more minutes on 150GB HDD.

what means this command?
or what free space consolidation means?

thank you.
sasanet.

free space consolidation takes all free sectors and such on your hard drive and arranges them together so they are contiguous. If you don't do that, it just means that some files could get placed into other blank areas between files and such on your hard drive. Hard drives are so fast these days, that I'm unsure as to whether bothering with free space consolidation would really make a noticeable difference.

thnx pparks1 for reply, I get it now.
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if may I, BTW your'e signature...
I like it very much however I dislike linux :/ (video/audio/instaling software sucks, but powerfull for hacking)