Simply put, website design is what your site actually looks like.
You can either
Learn how to code yourself - totally free but has a steep learning curve that requires dedication.
Pay someone else - sure it might look good but will it be worth the money?
Use the many free templates that come with your hosting package to do it yourself.
Design might be slightly limited but we're back to the advantage of being free, and without the learning curve of coding. We can even help get you started (again, for free!).