The Schulte Table (Schulte Grid) was developed by german psychiatrist and psychotherapist Walter Schulte originally as a psycho-diagnostic test to study the properties of attention. It is a grid (generally size 5x5) with randomly distributed numbers or letters. There are possible variations with different dimensions, coloured cells and values. Especially note there is a mode as the Gorbov-Schulte tables.
Positive effects include attention stability, improved visual perception, improved peripheral vision, development of speed reading and force a bit brain functions.
You can use it for training your brain or just for fun like a concentration game (with positive effect). There are different sizes, styles of grid and other settings, also you can check your stats with best results.
Speed reading training
Focus on the grid centre and find all the numbers (letters) with your peripheral vision, i.e. without moving your eyes.