A copy-edit is the second stage of editing and will check your facts and sentence structure for clarity and readability.
Imagine you are an agent or publisher and a manuscript lands on your desk.

The story is pacy and gripping but it is full of grammatical and/or punctuation errors. How long would you continue being able to read before the grating errors jar you from the story? This is where copy-editing is important.

While you should always use your computer’s automated spelling and grammar checks prior to submitting to your editor, it is important to remember that these automatic tools will only help the accuracy of your sentences to an extent.