My original thought was that it had to do with a DB query plan. ie: converting a SQL statement to a set of operations.
Reading through this, I came to the same conclusion. I am really confused as to what a plan is in this context.
My best guess is that it is similar to the DB query plans above. It sounds like given a set of composable higher-order functions and a problem, students can use those functions to solve the problem.
The "plan" they are referring to is an abstract one, about how to transform input/output on some data
Example: you make a REST API request, get back some data, and need to transform it and save it as CSV. What are the steps you take/functions you combine to do this?