A simple way to remember is remembering OIL RIG
Oxidation Is Loss in electron
Reduction Is Gain in electron
Fe + Cu2+ -> Fe2+ + Cu
Fe gets 2+, it looses electron charges, which translates to increase in positivity
therefore Fe (OIL) went through oxidation.
Cu gains two electron, mean it loose 2 net postive charge.
therefore (RIG) Cu went through reduction.