Hands down, one of the best features of Gmail is the ability to archive messages. In the past, if you wanted to keep an email message, you had to put the message in a folder (or sub-folder) that you created to store messages. Finding messages that you saved often turned out to be a chore and time consuming, especially if the message got parked in the wrong folder. If your message applied to move than one folder, you had to create a copy and file it.
Why Should I Archive Messages?