Definition - What does Bin mean?
Bin refers to a location where wine is kept or stored. These storage vessels are numbered to distinguish and record where a specific wine was stored within the winery. Numbering is a commonly used practice in the wine industry, which acts similar to the placement of lot numbers on other products. Wineries often use bin numbers on wine labels to differentiate between the various wine offerings produced by the same winery.
WineFrog explains Bin
The use of the term "bin" originated in Australia where it is still used by wineries for storing batches of wines bottles in numbered areas or compartments and later used in the labeling of the product for differentiation. You can actually see the implementation of this term on products produced by wine brands such as Penfolds and Lindeman's.
The term commonly has nothing to do with the wine itself or its quality, however, some wineries also use them for coding the variety of grapes used in their wines. "Bin End" is another term derived from the term "Bin", which refers to the last bottles of a batch from a Bin of a particular wine.