What holds down the artificial grass?

I want to know what are the things that hold the artificial lawn in place.

The short answer is infill and nails. When installing artificial grass, you will need to use nails along the edges of the artificial grass at 4-6" apart on average, then after the installation, you will need to put the infills onto the turf surface averaged at 2 lbs per square foot. By using nails and infills to install artificial turf, you are not only hold down the grass, but also minimize the possibilities of failures on the edges and seams. Especially for having the infills to hold down the turf will prevent the artificial grass surface from moving much during temperature change and make the entire area solid and secured.
You can find more installation details at this link: https://megagrass.com/pages/installation

We used glue and nails on holding down our artificial grass. It was installed on a plywood and we want to make sure that it will not peel off so we used those two.