Question

difference b/w maxima and minima in ydse?

Answer 1

in ydse, when crest of one wave falls on crest of another wave and trough of one wave falls on another wave, then there is maxima i. e. bright fringe.
but when crest of one wave falls on trough of another wave or vice versa, then there is minima i. e. dark fringe.

Answer 2

heightest point of sth( like function graph  frequency) is maximum and that is maxima