Abbiegen vs. einbiegen
Both abbiegen and einbiegen translate to to turn in English, but they focus on different parts of the driving or walking maneuver. While abbiegen emphasizes the act of leaving your current path or road, einbiegen focuses specifically on the act of entering a new road, path, or space.
Abbiegen
The word abbiegen means to turn off a road or to change your overall direction of travel. It is primarily used when the focus is on leaving the road you are currently on, and it is frequently followed by simple directions such as left or right.
An der nächsten Kreuzung müssen Sie links abbiegen.
(At the next intersection, you must turn left.)
Der Radfahrer ist ohne Handzeichen abgebogen.
(The cyclist turned without a hand signal.)
Wir sind zu früh abgebogen und haben uns verfahren.
(We turned too early and got lost.)
Wenn du den Fluss siehst, biege nach rechts ab.
(When you see the river, turn right.)
Er bog von der Hauptstraße ab, um dem Stau zu entgehen.
(He turned off the main street to avoid the traffic jam.)
Einbiegen
The word einbiegen means to turn into a specific street, driveway, or path. It is used when the focus is on the destination of the turn or the new space you are entering, and it is almost always paired with the preposition in.
Das Auto ist langsam in die kleine Einfahrt eingebogen.
(The car turned slowly into the small driveway.)
Bitte biegen Sie an der Ampel in die Schillerstraße ein.
(Please turn into Schiller Street at the traffic light.)
Der Bus bog schwungvoll in die enge Gasse ein.
(The bus turned vigorously into the narrow alley.)
Wir müssen gleich in den Waldweg einbiegen.
(We need to turn into the forest path in a moment.)
Als sie in den Hof einbog, sah sie ihre Freunde bereits warten.
(As she turned into the courtyard, she saw her friends already waiting.)
Summary
In short, you should use abbiegen to describe the general action of changing direction or leaving your current route. Conversely, you should use einbiegen when you want to highlight exactly which new street, driveway, or path you are entering.