What this exercise trains
Memory Grid shows a short sequence of highlighted tiles and asks you to reproduce it. Each cleared level adds a tile or expands the grid, so the load rises until you run out of lives.
What it exercises is visuospatial working memory — the ability to hold a layout in mind for a few seconds while doing something else. That capacity is one of the components psychologists measure in the working memory index of tests like the WAIS, though a single game is a much narrower thing than a scored subtest.
Training exercises are not a scored assessment. For a measured result across four reasoning domains, take the free IQ test, and see our methodology for how that score is worked out. More exercises are on the training page.