What is the purpose if the grid in collect earth?

To perform a Collect Earth assessment over a region you need two basic ingredients :

1. A Collect Earth survey ( which is built through a different tool called Collect ( https://openforis.org/collect ) using the Collect Survey Designer : here is a video explaining how to do it, it is a bit old so the interface has changed a bit but the concepts are the same )

2. A Sampling Design, meaning the grid of plots where the data will be collected. There are many ways to do that, the easiest of them would be using a Google Earth Engine tool called Grid Generator that lets you build the grid easily setting some parameters. See this video for more info : USING THE COLLECT EARTH GRID GENERATOR . Of course there are many ways to do the sampling design, systematic, random, stratified and a myriad others. For a simple survey you can start with a systematic sample over your area of interest.

Once you have the CSV file with your plots it can be included in the Collect Earth survey project file (*.CEP) and then you can start collecting data in the plot locations.

I am not sure if I have answered your question, if not please describe your issue with some more context.