Learning music intervals is essential to becoming a good musician. An interval simply is the distance between two notes. It's not quite as simple as it sounds though.
We measure these distances in terms of whole steps and half steps, and according to their position in the scale. While this sounds like it would make things harder, what it actually does is trains you to relate notes in a way that can be universally applied to all scales and positions.
In this lesson we cover the system of naming music intervals by their position in the scale. We use numbers instead of letters for this so that we can apply these names in all keys and all scales.
In this lesson, we'll combine the above system of naming intervals by their position in the scale with a system of naming them by their size. An interval's size is its distance from the lower note to the higher note.
Hope this helps! Practice hard and let me know if you have any questions!