Traditional guidance (including on this site) when creating a child theme has been to use an @import rule in style.css to import the CSS from the parent theme, so that you can then add your own style rules after that.
A recent post from Konstantin Kovshenin has had me rethinking that. He highlights that using an @import rule requires the two stylesheets (the child theme and the parent theme) to load in series rather than in parallel, which adds time to your page load speed.
To overcome this, he recommends enqueuing the parent theme stylesheets instead, so that the two files can download in parallel, reducing your page load time. You can drop this snippet directly into the child theme’s functions.php without needing to change anything:
Note that because WordPress loads the functions.php file of your active theme before going on to load the rest of the theme, having this snippet in functions.php will ensure that the parent theme CSS is still loaded before your child theme CSS (important if you want to redeclare any existing CSS rules).
Because the inclusion of the the parent theme’s CSS will only be of use while the child theme is active, it is very appropriate to put this function in the functions.php file of the child theme.
So, whenever you create a child theme in future, seriously consider enqueuing your parent theme’s CSS instead of @importing it.