Well you could start by simply typing "28 cm HE Rocket" into Google
http://en.wikipedia.org/wiki/28/32_cm_Nebelwerfer_41
The 28 cm Wurfkörper Spreng (Explosive missile) rocket weighed 82 kilograms (180 lb) and had a 50 kilograms (110 lb) high-explosive warhead. The 32 cm Wurfkörper Flamm (Incendiary missile) was normally filled with 50 litres (13 US gal) (45 kilograms (99 lb)) of incendiary oil (Flammöl), but could carry poison gases or decontamination fluids. The oil could cover 200 square metres (2,200 sq ft)[1] Both rockets were spin-stabilized and electrically-fired.
Or if you prefer it in German
http://www.lexikon-der-wehrmacht.de/...etenwerfer.htm
However, if all you want to know is why it's in an infantry unit it's becasue the Germans would drag the rocket and frame and point it at a target like a bunker or house and set it off. We get asked this question about once every two years.
Don