What is proofreading?
Proofreading is a final thorough check over your work before publishing.
Proofreaders check for spelling, punctuation and grammar errors and generally make the changes for you. Sometimes, editors will flag the errors and the writer makes the changes. The latter approach helps you learn about any tics or mistakes you make regularly.
Don't skip this stage. It's the last look before you send your work into the wide world. So it matters. Get it done professionally.