About GNU, GPL, LGPL,FOSS etc.

[tonnot]

I dont understand if I can or not use third soft components I'd want to add to my commercial application.
I read and read and read GNU and GPL (are the same?) and LGPL, BSD; MIT ... and I have not any conclusion (I'm very confused)
Starting at the point my appplication are going to be commercial, what can and cannot I do whith the 'free' licenses types ?
What about my own development ? It can exist two uses :
1.- I use third component (exe, lib + source code or full source code)
2.- I use full source code and I have modified some parts.

The check list is then :
--------- Use exe/dll ---- Full source code ---- Modified source code
GPL
LGPL
FOSS
MIT
BSD

And the answer for each item :
- Yes: You can use totally free.
- No1: You have to redistribute your whole own software
- No2: You have to redistribute only the modified original source code

And whats about the obligation to show copyright ?
- Yes : You have to show a GNU/LGPL/etc copyright text.
- No1 : You only have to inform that you use a third component by its name.
- No2: You have not to show no copyright neither references.

Can anybody fill the list ? Thanks