Series Name - Each robot company has its own approach to naming series or robot lines. Some series names are connected to application, such as Motoman's CR (clean room) robots. They can range from acronyms to entire words. Other manufacturers append letters to the end of the model name, such as FANUC's Toploader Series. These robots have the letter "T" appended to the end of their model name.
Model Name - Within each series, individual robots are distinguished by model names. Model names are typically associated with payload, like the Motoman SK 6, whose payload capacity is 6kg. Models are sometimes given even more distinction by adding an additional letter to denote specific characteristics of that robot. These letters can be related to mounting specifications, build, controller, etc. The FANUC R-2000iA/125L has a 125kg payload, but the L indicates that this robot is a long arm version.