As much as we love copy/pasting in our everyday life (job applications, anyone?), it can be a bit exhausting pressing Ctrl/Cmd+V over and over again to have the same drum pattern for an entire song. Therefore - the existence of loops!
Click the loop icon in the upper right corner of a region (1) and drag to the right. This creates shadow segments that mirror whatever is in the base segment (the original region). If you change the base segment, the shadow segments will change accordingly. Let the looping begin!
Check out this video for a clearer view.
(1) Loop icon in the top right corner of a region