Theta Music Trainer is an online ear training service. It covers everything from pitch, intonation, rhythms and recognising notes and chords within a scale. You can just play around with the games or it has courses that give some text slides to teach you and integrates the games into the learning. The focus is on training your ears; to be able to notice the small changes in pitch and differences in rhythms - this is more important than knowing music theory.
For the exercises that use a mic you will need to use earphones.
We have a school account you can use so that it you don't have to pay anything to have full access to this trainer. To get signed up or if you need help with your login send me an email lm@ecc.org.uk
If you'd rather learn the music theory side through a video rather than text I recommend this video. Again ear training is the goal, not music theory but I never said music theory isn't helpful.