It’s a grid template with a tiny navigation bar to ease visitors’ navigation. The impressive thing about it is the flexibility in the dimensions of grid items, hence the word Random. What this means is that the grid items don’t have identical dimensions. Thus, the visitor’s eye doesn’t get bored, as it would get if they saw a repetitious pattern. To put it simply, a less tired visitor equals more time on your site and work, and, perhaps, more conversions.