The Gmail layout is very similar to most other email layouts. You have folders on the left hand side and a list of messages on the right hand side (which takes up most of the screen).
When you go to Gmail, you are placed on the list of messages. You can use the Up and Down Arrow keys to move through the list, and Enter to open a message.
Press the Left Arrow key to move to the list of folders.
As with the list of messages, you can use the Up and Down Arrow keys to move through the list of folders and Enter to open a folder.
Press the Right Arrow key to move back to the list of messages in that folder.
If you get lost at any point, press G then I to go back to the Inbox.
Microsoft Edge and Mozilla Firefox work the same as above.
Note: Make sure that you have keyboard shortcuts switched on, if you haven’t already. To do this, press Shift + ? for the list of Gmail shortcuts. Then press Tab and press Enter on the Enable link. You only have to switch on Gmail keyboard shortcuts once on your account in your chosen Web browser.
Note: If you use a screen reader, you may need to switch off the “virtual cursor”. Press Insert (or Caps Lock) + Z in JAWS or Insert (or Caps Lock) + Space in NVDA.