Below I have covered the tabs shown when working with email - the tabs and their content change if you are working with Contacts, Calendar, Tasks or Notes

New |
Create a new email message, appointment, meeting, contact or task |
Delete |
Mark selected email as junk or delete it |
Respond |
Reply to or Forward selected email message |
Quick Steps |
Move messages, mark as read/unread, add to calendar and find messages |
Move |
Move selected message to a different folder - configure rules to automatically move messages depending on content/sender etc |
Tags |
Mark messages as read/unread, tag for further action or categorize |
Find |
Search for people in your address book or filter your email view using multiple criteria such as date received, sender, whether it has attachments etc |
Send/Receive |
Check for new messages with all configured email accounts |

Send & Receive |
Check for new messages with all configured email accounts or choose to just update selected accounts |
Download |
Shows progress of current mail operation - handy to check progress of sending/receiving especially if large attachments in email message - you can also cancel current operation |
Server |
Choose to download just message headers rather than the complete message |
Preferences |
Work offline - disconnects you from your mail server |

New |
Create a new folder to store your emails - or create a search folder which will contain results for your chosen search |
Actions |
Rename, copy, move or delete selected folder |
Clean Up |
Mark messages as read, clean up specific folders or delete all messages in selected folder |
Favorites |
Choose whether to show selected folder in Outlook favorites list |
IMAP |
Settings specific to IMAP connections - for choosing which folders to sync |
Properties |
Change settings to autoarchive emails and see properties/permissions of selected folder |

Current View |
Customize current view, and choose whether to show preview/reading pane |
Messages |
Show messages from same recipient as a conversation rather than as separate messages |
Arrangement |
Arrange messages by date, sender, size, subject, category etc |
Layout |
Choose layout of folder pane, reading pane and to-do bar - |
People Pane |
Choose whether to show people pane - which shows more information on contacts and allows connections to social networking websites |
Window |
Display reminders window and choose to open current item in new window or to close all windows |