Left hand window has disappeared

I seem to have somehow deleted the window on the left hand side that has the Title, Artist, Album etc listed underneath each other. It also has the album artwork at the bottom.

Can anyone let me know how I can get it back, please?

Ctrl Q

That is called the "Tag Panel".
Its default location is on the left side of the of the list of files, but it can be moved to the right, top, or bottom of the main window or used as a completely separate window.

See also ...
[LP] tag panel positioning is broken