Zone explanation in fortigate

Good day everyone.

What are zones -

With the help of zones, we can combine one, two, or multiple interfaces or VLANs into a single group which helps to reduce the policy while creating.
let's suppose we have 10 VLANs and all VLANs need to access the internet or want to communicate with each other then we need to create one policy otherwise we have
created 10 policies separately.

Is the above explanation good or not let me know if there is any mistake.

Question from my side -

If only one VLAN wants to go outside I mean towards the internet then what will you do.

thank you

umesh