what is the difference between distilled and deionised water?

Answer 1

Distilled water has been heated to boiling and the steam condensed to remove all non-volatile impurities (usually salts).

Deionised water is purified by passing through an ion exchange resin, which exchanges inorganic ions for HO- or H+. It is thus possible that depending on the water source the deionised water might have a different pH.

Answer 2

Distilled water is really pure water since then you evaporate water only water pure is obtained.
When you deionize water, you withdraw only ions and perhaps other minerals but it is not sur you get rid of organic materials