The grids are the vertical lines in the Editor area which let you see the bars of your project. In some cases you might need to zoom in to get a clearer view of what you're doing.
There are two ways of zooming in and out:
a) Use the magnifiers in the lower right corner in the studio (1). Zooming in automatically adjusts the grid resolution until it displays whole bars.
b) Use two fingers to zoom in and out if you have a touchpad!