This Google Slides presentation gives a thorough explanation of the basics of intervals: what they are, harmonic vs. melodic intervals, and how to measure them. (It does not delve into major vs. minor intervals; this will come in a later lesson.) It also includes a lesson script in the Speaker Notes embedded in the Slides file (you can view these in editing mode by going to Insert >> Show Speaker Notes; or in presenting mode by hovering your mouse near the bottom of the screen until the Toolbar shows up and selecting Notes).

I've used this presentation and lesson with my beginning band students as well as my high school musicians; it can easily be used for all secondary school ages in performing or non-performing music classes as new content or a refresher. I've personally used it for Distance Learning purposes and found great success, though it just as easily be used in the physical classroom. The animations of objects serve to enhance the learning experience while providing visual interest. There are also many slides with practice questions to assess student understanding.

I hope you find this useful! Please leave a review, and send me a message if you have any questions, concerns, or suggestions for the product.