If you’ve downloaded an awesome theme and want to make some changes to it, you should do so with a child theme, as opposed to editing the main (or parent) theme.
Why? Because developers can often update themes for bug fixes and design changes. If you make changes to the main theme and then install an update, you’re going to overwrite your hard work.
On the other hand, if you use a child theme to make CSS changes, only the parent theme will be updated. All of your changes in the child theme will remain.
Some professional theme developers are aware of the importance of child themes and will include one for you. Then, you can just update that child theme as much as you want without worrying about parent theme updates overwriting your changes.
If you have a theme that doesn’t include a child theme, it’s easy to add one. You can find instructions to do that in our comprehensive guide to creating a child theme.