Summons a drone at the target location for 6 seconds (600 range). The drone reveals and disables all invisible traps and wards within an 600-unit radius. (60 second cooldown). Additionally, your champion gains true sight for 10 seconds.
Players erroneously assuming that if the drone doesn't reveal anything in a brush that there isn't anything in the brush is currently working in the favour of Vision Wards, which are going undetected for longer periods of time than they might do otherwise.
With the removal of Oracle's Elixir, Oracle's Lens is now the only item that grants True Sight on Summoner's Rift.
Note that the drone itself does not grant true sight, except for revealing wards and traps. For a stealthed champion to be revealed, they must be within a radius of the champion with true sight (not the drone).