There is the traditional and the modern harvesting method.
Olives are traditionally harvested by hand, and the riper they are, the easier it is to separate the fruit. So you can just pick the olives from the tree. The same goes for the olive farmers in the producing countries, who often knock the fruit off the branches with rakes or sticks. The falling olives are caught by a dense mesh net. This harvesting method is mainly used in Greece, since the geomorphology of the country does not allow the use of machines. As a result, Greek olive oil is of better quality compared to other countries.
In Spain and Italy in particular, however, so-called vibrating machines are used, which briefly shake the trees. The olives then fall to the ground, being caught by a net again. However, the disadvantage of the otherwise more effective machines is that they can only be used on flat terrain and the olive tree can be injured.