Question

When ammonium chloride is dissolved in water, the beaker gets cold. Which type of reaction does this describe

Answer 1

It's an endothermic reaction.

"The difference is the energy from the water is actually required to help "break" apart the compound into it's dissociated particles. Because the water has to "put energy in" to breaking the molecule the energy has to come from some where (thermodynamics).
This energy input into the molecule is observed as an endothermic reaction and the solution feels cold."

That should help you understand.