A (Address) RECORD INFORMATION
These records allow hostnames to be resolved to IP addresses. The hostname is something you choose and the IP address is the location you want to point to.
A records are in the format of Hostname → IP address. (See example below).
From the above example, the hostname is set to 'office' and the IP address set to '192.168.1.50'. This is a valid A record. If this record was for the domain domainname.co.uk then it would mean that office.domainname.co.uk points to 192.168.1.50.
Host
Host can be a string containing alpha-numeric characters including hyphens. May be a single @ or * character to denote the primary record (i.e. domain without www) or wildcard respectively.
Can also contain a period between strings, (i.e. test.dev) but not at the beginning or end of a string.
IP Address
A records must be a valid IP address and cannot contain letters. 192.168.1.50 is valid. www.domainname.co.uk is not valid.
Wildcards
Wildcards in practice, if you need one, you should only use one entry in DNS. Either under the A records or the CNAME records – not both.