On w3schoolds they give you the grid layout information along with browser support. They then go on to explain grid elements, grid columns, grid gaps, display property, and more as well as giving example that you can try for yourself.
On this page it has a good guide to learn to basics of CSS grid and then it has visual examples of each topic it explains which could be very helpful to some. It goes more in depth with the grid properties with how to write it and how to see it in working form
On the site the give the basic run down of the CSS grid layout and then a basic example. Further on the page there are links that you can follow which will give you more in depth information about all of the properties, functions, data types, and guides.
All of the three sites that have been mentioned all provide very useful information. Some may be more viusal apealing like css-tricks.com and still provide information.