A more reactive element displaces a less reactive element from a compound, resulting in a new compound and the release of the displaced element. These reactions are often used to extract or obtain metals from their ores.
Example:
Reaction between zinc and hydrochloric acid:
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

In this reaction, zinc (Zn) displaces hydrogen (H) from hydrochloric acid (HCl) to form zinc chloride (ZnCl2) and release hydrogen gas (H2).

Double Displacement Reaction:

In a double displacement reaction, the positive and negative ions of two different compounds exchange places.
This type of reaction often occurs in aqueous solutions and can result in the formation of a precipitate (an insoluble solid), water, or a gas.
Double displacement reactions are also called metathesis reactions.
Example:
Reaction between silver nitrate and sodium chloride:
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)

In this reaction, the positive ions (Ag+ and Na+) and negative ions (NO3- and Cl-) in silver nitrate (AgNO3) and sodium chloride (NaCl) switch places to form silver chloride (AgCl) as a solid precipitate and sodium nitrate (NaNO3) in the aqueous solution.In summary, the key difference between displacement and double displacement reactions is that displacement reactions involve the replacement of one element in a compound, while double displacement reactions involve the exchange of ions between two compounds, resulting in the formation of new compounds and often the precipitation of an insoluble substance.