difference primary /secondary zone

Into DNS how can I resolve the name of my server?
what is the difference between primary and secondary zone?

Suppose that the name of my server is S1, I have done this:

I have created two zones (with zone type PRIMARY) one for each
subnets.Than I have assigned the zones to the relative subnets.
Then I have created a resource record with name S1 and ip equal
10.10.21.254 for the first zone.
Then under the second zone I have created another resource record with
name S1 and ip equal 192.168.3.4
Is it correct?
Is it correct to use the same name but different ip?

Is it correct to create the zones like PRIMARY and don't use "zone type
SECONDARY"?
What is the purpose to use zone like as secondary?

thanks
Regards,
Monica