In Google Sheets, rows don't really have an identity apart from their row number. In the image below we can see that the product Part 3 is located in row 4.
This is fine, but if you add, move or delete rows, that row's location will change. In the image below, Part 3 started off in row 4, but ends up in row 3 after we delete a row.
In some circumstances this is fine. But if you have Components like Comments and Favorite or use Relations—which need to know the exact location of a row and then the row number changes—these components will be confused or pull up incorrect data as they are only looking at row numbers.
Unique Identifier
The way to solve this issue is by giving each row a Unique Identifier. In other words, a value in a column that will always be different and unique for each row. And the easiest way to do this in Glide is by using the Row ID column in the Data Editor.
If you don't have a Row ID column in your table, components like Comments and Favorite will ask you to set a Key or a Topic. This is a manual way for you to connect that component with a column of unique values in your sheet so it can keep track of that row. The Row ID column is the best way of doing this.