Answer: Two planes intersecting in a line
Step-by-step explanation:
The wall and floor are two different planes. They meet up to form a line which is the crease between them.
A plane is a flat surface without any bends or curves to it. In theoretical terms, planes go on forever in all directions. Realistically there are limits of course. The wall or floor cannot go on forever.
Another example of two planes would be found in a book. Each page is a plane. Two adjacent pages meet up to form a line (i.e. the spine of the book is a line).