is a plane infinite in length and width?

if i define a plane by 3 points is that a plane that exists infinitely and those three points just happen to be 3 within it, or do those 3 points define the bounds of the plane?

It seems like that defines the bounds based on experimentation.

If so does anyone know if a plane which is defined not by 3 points but just by 1 point a normal (which since a plane requires 3 points at minimum to be of a defined size)
is infinite?

Planes are defined with 3 points, just like lines are defined with 2 points, and points are defined with 1. Just like a line is infinite ( Don’t confuse lines with line segments ), so too a plane is infinite. You ‘could’ use the tree point to define an outer bound, just like you can use two points to define a line segment.

Unity defines planes with a origin, and a normal vector. They are infinite in width.