CNAME and a record (address) difference

CNAME and a record (address) difference
A record is to parse domain name to Ip,cname is to parse domain name to another domain name.


A server can lay out multiple Web sites or multiple domain names, such as
such as Domain A----->a record-----> Real Server


Domain B (also known as a alias)
Domain C (also known as a alias)


If b,c at this time also through the form of A record to the real server, then which day the real server changes, a,b,c have to modify.


If the b,c is resolved to a, then if you modify it, you only need to modify a.


How to do it. The b,c can be resolved to a by CNAME.