The Panasonic Lumix 45mm 2.8 lens is a macro lens for Micro Four Thirds system cameras. It is co-branded between Leica and Panasonic, built in Japan under Leica management.
The lens has a hardware stabilization switch ("Mega OIS" in Panasonic branding). It also has a switch for focal range, to reduce focus hunting when macro capability is not needed.
Focusing is internal, so polarizing filters can be used consistently. The 46mm thread lets a Micro Four Thirds user share filters between it, the Panasonic 14mm, Panasonic 20mm, and Panasonic Leica 25mm & 15mm lenses.