Note: These figures change while emails are being sent out, opened and clicked.

Sent
Number of unique email addresses this email have been sent. This figure may be smaller than unique recipients of the email as invalid, non-working addresses and those with marketing ban are filtered out.
Opened
Number of recipients who have opened the email showing images such as your logo. Emails have a personalised tracking pixel that needs to be shown in order to register as an open. However as most email clients suppress images by default and require user to allow them for a new sender, this figure is highly unreliable especially for lists with many new recipients and between lists with different audience profiles e.g. private vs corporate.
Clicked
Number of recipients who have clicked at least one link in the email. This is reliable figure however not all clicks turn into views as inpatient users especially on mobile devices may not wait until the page loads.
Bounced
Number of recipients the email was sent but could not been delivered. If this happens for a permanent reason or repeatably for a recipient, the email address is closed out from further use by banning marketing with reference to reason. This keeps your list in good shape. In case of a temporary reason, the figure is not updated if the email is successfully delivered on a retry.

Expect high bounce rate if you haven't used a list for a while as people change jobs.

Most organizations close mailboxes when a person leaves the company, while some set an out-of-office autoreply which is not registered here. It's a good practice to checked bounced addresses here as well as go thru the out-of-office messages sent to the sender's inbox to see if a key person has left and a new contact should be found.

On the list view, the date and time is the first time email was opened, clicked or bounced, and is not updated on further opens, clicks or in case of later successful delivery.

If a recipient sees the email without images, open event is not registered, and thus it's possible to click a link on an email that recipient have not opened.