Grids

Grids can be turned on/off (visible/invisible) in the View Configuration panel.

click on image to view

Snap Grid, Snap Distance, Grid. Can't Set "Grid", What Does "Grid" Mean. - Altium Discussion Forums

That's it !

Working on the Grid

Component Grid

click on images to view

That's it !

Grid Settings - Easy on the Eyes

The default bright white grid lines and dots are a bit distracting and hard on the eyes. 

For a softer look that is easier on the eyes the color setting for the grid lines and dots can the adjusted.

Select Ctrl + G to bring up the Cartesian Grid Editor dialog.

As shown I have set the Dots to a med gray (color 34) and the Lines to a light shade of black (color 38).

Here is what the results look like.
Click on Image to View