The September issue of the *Notices of the American Mathematical Society* is out, and the highlight is Robert Gompf’s 3 page introduction, WHAT IS… a Lefschetz Pencil?.

The WHAT IS… series is a terrific addition to the magazine, which began back in September 2002 with WHAT IS… an Amoeba?. Since then, it’s provided quick introductions to various terms that float around mathematics, such as the Monster group, motives, flips, and even operads.