Archiving in Gmail is very different from archiving in GroupWise. In GroupWise the archive was a separate folder that items were moved to. In Gmail archiving remove the inbox label from a message.
All items in the Inbox actually have an inbox label applied. This label isn't show when you are in the Inbox, but it can be seen by selecting the All Mail view from the left list of options. The All Mail view will show all items in your mailbox and any associated labels.
When you archive an item it removes the inbox label, but leave all other labels intact (if there are any), so items marked with a personal label that are archived can be viewed under All Mail or your Personal label. If the item has no labels applied when it is archived it can only be viewed by either searching for it or through All Mail.