This is a screenshot from inside of Google Classroom.

As you can see, something has been attached to this assignment but the student has NOT clicked the 'Turn in' button.

This is a screenshot from inside of Google Classroom.

As you can see, the word 'Turn in' has been changed to 'Unsubmit'. This shows the student has clicked the 'Turn in' button and is ready for the assignment to be graded. You can click on the attached file (in this case it is a screenshot) to see what the student submitted.