Final answer:
A metal being added to the salt solution of another, resulting in the displacement of the latter, is called a displacement reaction, a type of oxidation-reduction reaction influenced by the activity series of metals.
Step-by-step explanation:
The reaction described in the question, where a metal X is added to the salt solution of metal Y and causes metal Y to be displaced, is known as a displacement reaction. This type of reaction is a subset of oxidation-reduction reactions, or redox reactions. During the displacement reaction, one element (metal X) takes the place of another element (metal Y) in a compound, leading to the formation of a new compound (solution of X) and the release of the replaced metal (metal Y). An essential aspect of this reaction is that it involves the transfer of electrons from one metal to another, indicating an oxidation-reduction process. Metals higher in the activity series can displace metals lower in the series from their compounds.