Frame is environmental, or structural framing, framing with light or lack of light, they all work well to bring the viewer's eye to your subject it is some what defined as 'a technique used to bring focus to a subject'.
In This photo I took, the trees work as a frame putting the person in the centre it adds some what detail and makes you drawn to the person . You can use bridges arches many different things,although the trees don't frame around the whole photo its still framing.