Slide left on the top filter bar to browse through filters and choose an option to narrow down the amount of emails from any folder or tap on Customize, at the end of the line, to rearrange the order of the filters by dragging Drag icon them up and down.

Unread - Shows recent unread emails.
Starred - Brings up emails you have starred.
Travel - It will list upcoming, past or travel related emails.
Attachments - Shows all the attachments in the folder which you can sort out further using the Filter icon Drag icon.
People "Android Only" - Sorts out emails from top contacts or tap on View all to have them sorted alphabetically or by business.