Hal(ogen)ide ions are resulting from reactions of the halogens fluorine, chlorine, bromine or iodine with hydrogen or with metals. Silver nitrate solution is a reagent for them.
* Put drops of the following solutions on a plastic sheet: Hydrochloric acid  [HCl(aq)],   table salt [NaCl(aq)], barium chloride [BaCl(aq)], iron(III) chloride [FeCl₃(aq)],  copper(II) chloride [CuCl₂(aq)], tapwater treated with chlorine.
* Add a drops of silver nitrate to each of these solutions.
Observation (Photo): Each time the transparent liquids react forming a white, yellow or blue solid.
Explanation: Each time a white solid of silver chloride is formed.
The respective solid silver salts can be seen when you test for fluoride, bromide and iodide ions.