An interval describes the distance between two notes, including the notes themselves.
The ability to recognize intervals within music is speed reading!
A 2nd is always a line note and a space note set down beside each other diagonally.
A 3rd is either two line notes, or two space notes stacked up.
A 4th is a line note and a space note, and a span of four keys on a piano keyboard.
A 5th is two line notes or two space notes making a span of five keys. A 5th fits perfectly using the thumb and the pinky finger.
A 6th requires a slight stretch of the fingers to span six keys.
A 7th is always two line notes or two space notes, and easy to recognize because they cover so much ground.
An 8th is also called an octave. An octave means: same note, eight notes apart.
Learn to recognize notes and intervals like old friends! Make the leap from beginner to early intermediate using the Read Music Method for Adult Beginners.