The Pipeline is a term that describes the application and file interchange backbone of your production workflow. Small shops usually have a very informal pipeline, managed by the same people who create content elements and assets. Larger shops have staff dedicated to the pipeline, as it is the single most vital component of a smooth CG production. Without a strong, reliable pipeline, you will experience delays, data loss, and worse. Even with a pipeline and a dedicated staff, you may still experience these issues. Fortunately, a dedicated staff gives producers someone else to blame, and sheilding you from such an unfortunate position.
There are various aspects of the production pipeline, just as there are several aspects of CG production. Asset management is one of the mostr critical aspects of the pipeline, in addition to the traditional information technology-related functions (as in, keeping everyone operating smoothly, data backed up, and so on). Another aspect is the facilitation of the rendering pipeline, often separate from the overall pipeline to insure rendering reliability.) The pipeline often requires scripts written in Python to facilitate automated functions; glue code (translations) for inter-application communications; code to drive compositing node trees on the fly; loading and unloading of compute and disc resources; rendering control; and so on. Feature film pipelines are by far the most complex you are likely to encounter.
If you are lucky enough to have dedicated staff for pipeline support, thank them. By them coffee or a danish. Give them a car. Whatever it takes, theirs is a high-pressure position, and good pipeline management staff are worth their weight in gold. Without them, nothing can happen.