You use reasoning to propose a process that explains observed facts. you use reasoning to propose what facts you would observe if a known process took place.

You use inductive reasoning to propose a process that explains observed facts. You use deductive reasoning to propose what facts you would observe if a known process took place.

Deductive reasoning, or deduction is a type of reasoning used in scientific method. It starts out with a general statement (called hypothesis is scientific method), and examines the possibilities to reach a logical conclusion about it. If the theory is correct, what observations should be.  Inductive reasoning is the opposite. It is a type of reasoning when you start from specific observations to the general statement.