I do not think that rephrasing https://en.wikipedia.org/wiki/Differential_algebraic_equation would be efficient. Please read this an ask a specific question, if any detail does not become clear.
Searching in the net for "Differential algebraic equation" will reveal many other sources to get explanations from. Reading, what has been written already, is more efficient than letting another user of the forum answer this very general question. You can even write books about DAEs.
