What is Rooting, and Why you should or shouldn't care? (Updated 28-10-11)

I used Super1Click 2.1.1 to root my GT-i9000M last night.

Maybe he/she needs to get the newer version?

I'm using a notebook,too. Vista, Ubuntu and Linux Mint on it.
To flash a ROM:
- your phone should be SIM unlocked.
- you need to use the 3 button combo.
- rooting: you should flash the Speedmod_k13E.tar as PDA in Odin.
To get to download mode use the ADB method!

Ok.

I have been searching the 'Net for two weeks trying to find out how to root my phone.  I think I have 'found the place'.  I certainly hope so.  Here is what I think I know:

Samsung Galaxy S 4G from T-Mobile USA

From SETTINGS/ABOUT PHONE
Model SGH-T959V      <<<<<<<<<<<<???????
Firmware:  2.3.6
Baseband T95VUVKJ6
Kernel 2.6.35.7-T959VUVKJ6-CL694130
Build number Gingerbread.VUVKJ6

From stickers on product BOX:
Samsung Galaxy S 4G
8 GB expandable to 32GB
5 megapixel camera
SAM T959V GALAXY S 4G REFLEX SILVER KIT
Kit SKU 610214625717
Handset IMEI 357982044973525
Untitled tag 000000610214625717
Untitled tag RS 170-6157
SIM Serial # 8901260531589381839F
BAN number 245687643
TGT 170-6157 Made in China
Model #: SGH-T959HABTMB   <<<<<<<<??????????

I am VERY new to Smartphones.  My main goal is to root so that I can uninstall bloatware .. though the other advantages are also desireable.  I would also want to know how to UNroot in the event that I would need to send it back to T-Mobile (or would it be Samsung?).  ALSO, I read somewhere that rooting a phone CAN prevent 'online' updates ... from Samsung or 'whoever'.  By that, I mean (for example) when/IF an upgrade from Gingerbread to Ice Cream Sandwich is ever 'offered' .. I would certainly like to have it ... I would think .. though I read about that being possible through other means already.  More confusion .. actually.  

Back though, to priorities .. get this phone rooted and get rid of a load of bloat .. yet be able to get 'official' updates/upgrades .. which I assume means I will have to be able to UNroot.  I dunno .. to be honest.

Other issues I have read about ...

LAG ... but from what I understand this does not apply to Gingerbread as it uses EXT 2 or 4 ... can't remember which at the moment.  Maybe LAG does apply .. dunno .. more confusion.

Fashing ROM.  From what I have read .. not sure what that would do for me.  I THINK I read that 'flashing a rom' can result in a ROOTED phone .. but at the same time .. changes a lot of other things.  I sort of don't think doing so is something I entertain ... more confusion.  I also 'get the idea' that in order TO root, I will need to flash ... and I am not too clear on what the result of that is ... more confusion.

So, .. here I am .. hoping to uninstall some bloat .. and do not know what my next step is.  Obviously it would be to go to a thread that tells me what to do next .. but for some reason .. I don't think I am quite ready for that.  Still too much confusion.

For what it's worth, I have both an XP 32-bit and a W7 64-bit machine available to 'do the deed'.

Thanks in advance to anyone who can help me move forward.

EDIT:  Did I post in the wrong thread?  If so, please let me know .. and what to do aboutit (repost, have thread moved by moderator .. whatever).