Hello Elizabeth,
That icon means you have student submission and need to review them and score them.
If this is an Assignment, you need to score them in Speedgrader.
If this is a Quiz, you likely have a question that cannot be automatically graded by Canvas (for example Essay Questions) -- you'll need to go through and Grade those questions.
Click on the Assignment of Quiz name at the top of your grade column to go to the Speedgrader.
You might also see a To Do list on your course's home page (right hand side) that tells you you have Grading To Do. That's a quick way to get there.
Here are some Canvas Guides that can help:
