[Q] Travelling to Indonesia. About CSC Codes

Hi,

I'm travelling to Indonesia this summer and want to use an Indonesian SIM whilst I am out there. Using GalaxSim, I can tell that my phone is network unlocked, however it says that CSC Lock is 'locked'. I live in the UK and know the CSC on my phone is BTU, as I has previously flashed with a BTU firmware.

So two questions,

a) What does CSC Lock 'locked' actually mean?
b) Will I be able to put an Indonesian SIM in with no issues?

Thanks.