Inbox is where all incoming mail is placed, unless Filters move messages to a custom folder, archive, or delete it on arrival.
Outbox is where unsent messages are placed while they are queued for delivery. After the messages physically leave the system, they can be found in Sent folder.
Draft contains messages saved as draft. Drafts are saved automatically as you compose a new message.
Sent displays all sent messages. You can filter sent messages by user who sent them.
All Mail contains all incoming email, whether it was archived or is also located in a custom folder. It does not display sent or deleted messages.
Trash is where messages are moved when deleted. These messages do count towards your disk space usage until you purge them from the Trash folder. Messages in Trash are automatically purged every 30 days.
Spam This folder is where messages marked as spam are placed.
Bounced If the Bounced feature is enabled in Settings > Department, email messages returned as undeliverable will be placed in this folder.
Newsletters This folder will display all sent and scheduled email newsletters to groups of contacts. You can monitor sending progress or cancel current or scheduled sending.