Email forwarders allow you to forward a copy of all mail from one address to another. For example, you could set up a forwarder to forward all mail received on info@mysite.com to admin@mysite.com.
info@mysite.com will still keep the original version of all messages it receives, and admin@mysite.com gets forwarded a copy.
It's worth noting that this relationship doesn't work in two directions. Mail received by admin will not go to info.
Another type of forwarding is a domain forwarder. This will forward all mail received on a specific domain to another domain. If we forwarded mysite.com to demosite.com, admin@mysite.com and info@mysite.com would be forwarded to admin@demosite.com and info@demosite.com, respectively.
The last kind of forwarder we'll mention is a "catch-all" or default email address. With this kind of forwarder, mail sent to an email address that doesn't exist will be forwarded to the email address you specify.