A reference task is a certain task, which has a fixed amount of story points assigned, and which is used as a reference point to estimate other tasks. But how do you choose such a reference task? This post should give you a method and some ideas, how you can find a good reference task.
As a side node – I use the word task here for every type of work item in a sprint. So user stories, backlog items or whatever you call it – here I always use the word task.
