CSS for different versions of IE web browsers

I have read an article about the explanation of the IE version, and I can understand it. I 'd like to write it down. it is hard for me to understand that "CC" is short for "Conditional Comment? Please let me know. Thank you.
The explain statement is as follows:
Gt = selects greater than (higher)
Lt = selects less than (lower)
Gte = selects greater than or equal to (> =)
Lte = selects less than or equal to (<=)
! = Selects everything failed t what directly follows "! "(Select all, !)
I don't know why there is no way to display the explanatory symbol on the csdn page, so I just omitted it !!!!!!!
1. For IE5.01, you can use "if ie 5.0", "if Ite ie 5.0", or "if! Gt ie 5.0 "or" if lt ie 5.0000 "or" if! Gte ie 5.5000"
2. Select IE5.5, IE6.0, and IE7.0. You can use "if! Ie 5.0 "or" if gt ie 5.0 "or" if! Lte ie 5.0 "or" if! Lt IE 5.5000 "or" if gte IE 5.5000"
3. Select IE5.5 and use "if ie 5.5000"
4. Select IE 5.01, IE6, and IE7.0. You can use "if! Internet Explorer 5.5000"
5. Select IE 6. You can use "if IE 6"
6. Select IE 5.01, IE5.5, and IE7.0. You can use "if! IE 6"
7. Select IE 7.0. You can use "if IE 7.0" or "if! Lte IE 6 "or" if gt IE 6 "or" if! Lt IE 7.0 "or" if gte IE 7.0 "or" if! Lt IE 7 "or" if IE 7 "or" if gte IE 7"
8. Select IE 5.01, IE5.5, and IE6. You can use "if lte IE 6" or "if! Gt IE 6 "or" if lt IE 7.0 "or" if! Gte IE 7.0 "or" if lt IE 7 "or" if! Gte IE 7 "; or" if! Internet Explorer 7.0 "or" if! IE 7"
9. Select IE 5.01 and IE5.5. You can use "if IE 5", "if lte IE 5", or "if! Gt IE 5 "or" if lte IE 5.5000 "or" if! Gt IE 5.5000 "or" if lt IE 6 "or" if! Gte IE 6"
10. Select IE 6 and IE7.0. You can use "if! IE 5 "or" if! Lte IE 5 "or" if gt IE 5 "or" if! Lte IE 5.5000 "or" if gt IE 5.5000 "or" if! Lt IE 6 "or" if gte IE 6"
11. Select IE 5.01, IE5.5, IE6, and IE7.0, use "if lte IE 7.0" or "if gte IE 5" or "if gte IE 5.0" or "if lte IE 7" or "if IE ";
12. No IE 5.01 or IE6
13. No IE 5.01 or IE7.0
14. No IE 5.5 or IE6
15. No IE 5.5 or IE7.0