A function is not a design pattern. A design pattern is a design that solves a problem. Without stating the problem to solve, you have not got a pattern. The OP stated that they used functions to organise their code, so you can imagine some problem that they were solving with functions. For another problem you might solve with functions, I was reminded recently that functions are an implementation of the state monad. If you read up about where you might use the state monad and why you need it, then perhaps you can get a better feeling for why a function is a good implementation of that pattern.
