Turbo map reading for dummies

As i am a dummie, and i don't know how to read a turbo map, i found some links to help the guys wich are at the same level of mine.

so here is the link : compressor map reading for dummies

and another one : how to read a turbo map

I still don't get it. All I know is it goes whoosh and your off !!

the most simple to understand is the second link

but by my side, i bought a gt2860RS (you can see the map on the garrett website), it is efficient from 1bar (15psi) to 1.5 bar (22psi) and i can get from 260 to 300bhp max and it is advertise for 360 bhp max.....so i believe the things you put beside of the turbo (IC, exhaust..) will increase the base bhp you can achieve with the turbo....(that's i believe and i understand....)

am i wrong?

But, what i don't understand is where to see if it spool fast or not...??? maybe the size of the exhaust wheel?