What is the command to copy files from A to B when ssh connected?

[joe at actionline.com]

> joe at actionline.com wrote:
>> What is the correct command syntax to copy files from computer A
>> to computer B when ssh logged in to comuter B from computer A?

> That depends. Is name resolution set up, or do you need to specify an IP
> address when referencing the other computer? What ssh command did you
> use to log in to computer B?

I don't know what "name resolution" is (or how to set it up).
This is the ssh command I use to login:

ssh domain at box123.hostname.com