Step-by-step explanation
When a copper (Cu) wire, for example, is introduced into an aqueous silver nitrate (AgNO3) solution, a single replacement reaction occurs (when 2 elements in a reaction swap places, one replacing the other. This is a type of redox reaction)
In the beginning, the pure Cu is oxidized by the silver nitrate solution.
The opposite process happens to the silver nitrate, it undergoes reduction.