A contour is the shape in which the pitch of a melody travels.
There are four basic contours: arch, wave, inverted arch, and pivotal.
In an arch contour, the pitch goes up then down:
Figure 1: An arch contour.
In a wave contour, the pitch goes up and down repeatedly:
Figure 2: A wave contour.
In an inverted arch contour, the pitch down then up:
Figure 3: An inverted arch contour.
In a pivotal contour, the notes remain stationary around a certain pitch:
Figure 4: A pivotal contour.
Also see Phrase | Lyrics.