Forwarders work like this...
Say you have 5 e-mail accounts all for diffrent reason. EX. useradmin

yourhost.com , techsupport

yourhost.com , helpdesk

yourhost.com , iamabanana

yourhost.com , wyatturp

yourhost.com but instead of having to check 5 diffrent Inboxes, you can have them all forwarded to one main account like mainaccount

yourhost.com
I hope that helps