Shapes of screw head
(a) pan, (b) button, (c) round, (d) truss, (e) flat, (f) oval
pan head: a low disc with chamfered outer edge.
button or dome head: cylindrical with a rounded top.
round head: dome-shaped, commonly used for machine screws.
truss head: lower-profile dome designed to prevent tampering.
flat head or countersunk: conical, with flat outer face and tapering inner face allowing it to sink into the material.
oval or raised head: countersunk with a rounded top.
bugle head: similar to countersunk, but there is a smooth progression from the shaft to the angle of the head, similar to the bell of a bugle.
cheese head: disc with cylindrical outer edge, height approximately half the head diameter.
fillister head: cylindrical, but with a slightly convex top surface.
socket head: cylindrical, relatively high, with different types of sockets (hex, square, torx, etc.).
mirror screw head: countersunk head with a tapped hole to receive a separate screw-in chrome-plated cover, used for attaching mirrors.
headless (set or grub screw): has either a socket or slot in one end for driving.
Some varieties of screw are manufactured with a break-away head, which snaps off when adequate torque is applied. This prevents tampering and disassembly and also provides an easily-inspectable joint to guarantee proper assembly.