Two kinds of purpose or teleology: Intrinsic and extrinsic

From The Imagined Conflict, chapter 5 "Philosophy of Science"

If you think of why a carpenter makes a dinner-table, Aristoteles's four explanations are: 

1. the wood which is the material cause, 
2. the idea or blueprint which is the formal cause, 
3. the carpenter who shapes the wood and this is the efficient cause. 
4. The final one is that the table is being made because someone ordered a table for a big feast. This is the final cause, which has to do with purpose or intention. 

Explanation in terms of final causes is called teleology.