Angle-of-view is measured in degrees of arc. Objects outside the AOV when the picture is taken are not recorded in the photograph.
AOV varies according to the image format and the focal length of the lens, with small formats and short lenses giving the widest angles. A wide angle captures more of a scene than a narrow angle. Below are angles of view for lenses of various focal lengths using 35mm film.
NB the shorter the focal length the wider the AOV.

Full-frame
Lens   -  AOV
50mm -  46.8º
48mm -  48.5º
45mm -  51.4º
40mm -  56.8º
38mm -  59.3º

Half-frame
Lens   -  AOV
32mm -  50º
30mm -  53º