If you delete any message from your Inbox it still appears in your Gmail because those deleted mails are sent to the Trash where it remains for 30 days and after that gets automatically deleted.
You might feel the need to periodically or immediately delete Trash folder by yourself without actually waiting for the Gmail to delete it. This can be done very easily and without wasting much of time.
Steps to Delete Trash in Gmail
Step 1: Go to gmail.com and enter your login credentials viz User name and Password
Step 2: Go to “Trash” on the bottom left panel.
Step 3: You will find all the mails which you have deleted, select all the mails present in trash by checking on the box at the top left of the screen.
Step 4: Now click on “Delete forever” button at the top of the screen. Now your trash mails are deleted permanently.