Ear training is very important to the learning musician. Many jazz musicians learn to play by ear which is as natural as learning a language. Meanwhile, other musicians learn theory and read music, they sometimes forget to train their ears to recognize the notes, chords, rhythms and intervals that they hear. Both are great to do so that you know what you hear as well as understand how the music works.
Hear Chords and Their Specific Tensions
Hear Rhythm and it's Nuances
Here is a wonderful free online
for ear training intervals, chords, scales.