In a word, frame is the window on the parent view that sees the child view, and bound is the content that can be seen by the parent view on the child view.
A little explanation. Frame refers to the position and size of the child view in the parent view. Consisting of two parts, the first part is Origin, which specifies the location of the child view in the parent class. The second part is size, which refers to the visual range of the view in the parent class (in this case, the size of the view). It feels like a window is opened in the parent view at the Frame.origin location, the size of the window is frame.size, and the contents of the child view are visible from the window.
Bound refers to the view itself shows those content , Bound composition and frame similar . Also use the window to illustrate, at this time the handle view as a very large oil painting, in the parent view opened a window, but this window is pasted paper, only by the painting on the window. So, the final window shows what is decided by bound, bound decide which part of the painting.
Finally, for example, the picture on the right is what is actually seen, and in fact it is the content shown on the left. The shaded portion of the left image is the part of the Childview that is not displayed.