Deductive reasoning is reasoning that starts with a given set premises and draws a conclusion. Inductivereasoning is reasoning that draws a general conclusion based on a set of examples. So deductive reasoning goes from general principles to specific conclusions. Inductive reasoning goes from specific principles to general conclusions. Both forms of logic are used in science.
Deductive and Inductive reasoning are different and even opposite concepts but in practice deductive and inductive reasoning are often used together even without knowing it. For example one may be drawing a general conclusion form observed evidence (induction) based on general principles called assumptions. (deduction)
Logical fallacies are mistakes in reasoning and can be both deliberate and accidental. It is important to avoid them since they resultant in erroneous conclusions.