Responsive
The page adapting to phone size instead of showing up shrunken. It matters because nearly everyone looking for you is on a phone.
A responsive page is not the same page made smaller. It rearranges what it has: the menu becomes a button, columns stack, and text grows so it reads without pinching.
The most common problem in local business sites is stopping halfway: text reads fine on a phone, but the number sits under a photo that eats the whole screen.
Google judges your site by the phone version, not the desktop one. If it is slow or ugly on a phone, that is the one that counts.
What to do about it
Open it on your own phone, not on the computer. It is the only test that counts.
Other words about the same thing