just a few basic questions

[William Gacquer]

I am new to bind. 

I just changed the IP address of www.mydomain.ext, and restarted bind.
Locally,
     dig www.mydomain.ext 
works and shows the right (new) IP adress.

Remotelly, ( from your place, for instance ), the name is not correctly resolved and points to the old value.

Is this a DNS feature ?
Do I have to wait TTL seconds to see my IP address exported to external DNSes ?

Sorry for this beginner question.

William