To put it simply, redox (reduction/oxidation) reactions are a transfer of electrons. In it's most simple form, as a half equation, Cu -> Cu2+ + 2e-. Or as a complete reaction, Zn + Cu2+ -> Zn2+...
Yes, all combustion reactions are redox reactions because elemental oxygen is a reactant. (Silberberg, "Chemistry The Molecular Nature of Matter and Change" Fifth edition)