An oblique wing is a variable geometry wing

Swing-wing

A variable-sweep wing is an aeroplane wing that may be swept back and then returned to its original position during flight. It allows the aircraft's planform to be modified in flight, and is therefore an example of a variable-geometry aircraft....

 concept. On an aircraft so equipped, the wing is designed to rotate on center pivot, so that one tip is swept forward while the opposite tip is swept aft. By changing its sweep angle in this way, drag

Drag (physics)

In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

 can be reduced at high speed (with the wing swept) without sacrificing low speed performance (with the wing perpendicular).
The oldest examples of this technology are the unrealized German aircraft projects Blohm & Voss and P.202 Messerschmitt Me P.1009-01 from the year 1944, based on a Messerschmitt Patent.