Three points are coplanar.
Answers
This is exactly why two points are “always” collinear.
A (straight) line is “defined” by two points. Whether a third point is collinear to the line defined by the first two depends on whether the line defined by the third and the first/second is the same line or not. A line cannot be defined by only one point.
A (flat) plane is defined by three points. Whether a fourth point is coplaner to the plane defined by the first three depends on whether the plane defined by the fourth and the first and second/ second and third/ third and first are on the same plane or not. A plane cannot be defined by only two points.
A plane can also be defined by two intersecting lines. Any point on the first line except the intersection, any point on the second line except the intersection and the intersecting point is the unique plane. A plane cannot be defined by only one line. Two intersecting lines shall “always” be coplaner. Whether a third line is coplaner with the plane defined by the first two depends on whether the plane defined by the third and the first/second lie on the same plane.
In fact three collinear points do not define a plane. Three points are not “always” coplaner. They are, only when they aren't collinear.