One point many rays
Light will reflect off any point of a surface and travel in many directions. If you put a convex lens in the way, some of these light rays will enter the lens from points all over its surface.
A tree at a large distance from the convex lens will pass light rays into the lens. The convex lens can form an image of this tree, upside down, on a piece of paper (this will be explained later).
Each point on the object will reflect light rays onto the convex lens.
Light from a point can meet at another point on a piece of paper the other side of the convex lens.
For every object there are numerous rays being sent into the convex lens at many angles but all these rays can become focused back into one image, but upside down.