What are variation technique?

What are variation technique?
There are many ways composers use variations on a melody. A few of the most common ones are to change the accompanying chords, place the melody in a lower register with another melody or bits of melody happening above it, and to change the rhythmic patterns but keep the notes of the melody the same or similar. Sometimes you will hear the composer switch from a major tonality to a minor tonality or vice versa. There are as many ways to vary a melody as a composer has imagination (I think that's why they like the challenge.)