A Record

A records (also known as host records) are the central records of DNS. These records link a domain, or subdomain, to an IP address.
A records and IP addresses do not necessarily match on a one-to-one basis. Many A records correspond to a single IP address, where one machine can serve many web sites. Alternatively, a single A record may correspond to many IP addresses. This can facilitate fault tolerance and load distribution, and allows a site to move its physical location.
Google Apps does not support IP addresses alone. Instead of using A records, you can set up email and web publishing by modifying your MX and CNAME records with your domain host.