A Turnout (or Set of Points or Switch) is an Advtrains node that splits a track into multiple track (or combines two tracks into one).

A screenshot of a junction using Turnouts is below:

As you can see, there are many types of turnout.The first type is the straight turnout, which is accessible by left-clicking using the trackworker on an ordinary straight track. This turnout keeps one track straight whilst adding another at 30° either to the left or right. You can see that 4 are used in the T-junction.

The second type is a Y-turnout, which splits one track into two, one +30° and another -30°. You can see 2 of these used in the T-junction.

The third type, not pictured, is the 3-way turnout. The 3-way is much like the y-turnout but with an additional third track in the middle for keeping straight. This kind of turnout is exceedingly rare in real life - note the mechanism which moves 4 moveable blades instead of the ordinary two; so realism-focused players should generally try to avoid it.

Advtrains track is available in rotations of 0°, 30°, 45° and 60° from the axis - approximately. The actual underlying system is that there is a track that travels 2 metres along one axis to every metre on the other axis, as well as 1:1 and only along the axis. Using trigonometry reveals the actual angles to be asin(1/2) ≈ 26° and atan(2) ≈ 63°. But the numbers 0, 30, 45 and 60 are always used to refer to those rotations.

You will notice that since there is no constant difference of angle on the turnouts, that the 30° and 60° rotations of the Y-turnouts are not symmetrical. See the below picture.