Iphone 4 GSM carrier? What? - 1

I'm getting this iPhone 4 from eBay, and I want to use my telstra sim with it, but really I don't understand if this is capable. Here's the writing:

Apple iPhone 4 16GB

Factory Unlocked

Black

Will work on any GSM carrier worldwide that uses SIM cards. T-Mobile and AT&T in the USA.

Factory unlocks are the best because you can update the software or restore it without losing the unlock.

GSM is basically another name for a 2G SIM-card based phone, and as they upgraded to 3G, 4G, etc., they also upgraded the services used, such as GPRS (General Packet Radio Services), EDGE (Enhanced Data for GSM Evolution or EGPRS).

3GPP are known as UMTS; 4G is now LTE Advanced. "GMS" is a licensed product of the GMS Association.

Yes it will work with any gsm carrier.