So T-Mobile unlocked my old iPhone 5s but I have questions...

[iTone]

Does that mean the iPhone can now be used with any carrier, both gsm and cdma?

Just wanna make sure that is the case because someone on Sprint wants to buy it off me.

When I connected the iPhone to iTunes it said "Your iPhone is now unlocked." Is that the only way to confirm it?

 

[EDH667]

It is unlocked for only other GSM providers, not CDMA providers. Besides the message, you can also confirm that it is unlocked by using an AT&T or other GSM SIM.

 

[Applejuiced]

Only gsm for iPhone 5s.
The iphone 6 can be used on Verizon also when unlocked. Not sprint.

 

[iTone]

Could it also be used with GSM carriers outside the US?

 

[perkedel]

Could it also be used with GSM carriers outside the US?

Find out which model you have and match it with this list
http://www.apple.com/iphone/LTE/
it'll tell you where it'll work.

 

[Applejuiced]

Could it also be used with GSM carriers outside the US?

Yes.
Any gsm carrier in the world.

 

[corys00]

Only gsm for iPhone 5s.
The iphone 6 can be used on Verizon also when unlocked. Not sprint.

The 6 can be used on Sprint as well, it just won't have access to band 41 (Spark)