An interval in music is the distance between 2 different notes. If you can learn to identify different intervals when you hear them, you will take a big step toward being able to learn songs by ear, improve your guitar soloing ability, and much more.
For more information about the music theory of intervals, and how to play them on the neck of the guitar…check out this guitar lesson.
If you are new to guitar ear training, you might want to start out slow. Pick 2 intervals to work on. I would start with a P5 (perfect 5th) and a M2 (major 2nd). The best way to get used to the sound of an interval is to associate it with a common song.
In the guitar interval ear training program at the bottom of the page you will see a “learn” button for each interval. Press it to open up a window that shows some info about the interval, as well as a common song you can use to help learn the sound of that interval.
There is one song for ascending, and one for descending. Most of the time the interval is the 1st 2 notes in the song. If it is not the 1st 2 notes, then there is a bracket to indicate which notes make up that particular interval. You can listen to the song, or even try it out yourself with the supplied notation and tablature.
As you get comfortable with 2 intervals, start adding others one at a time. Start out melodically ascending, then work on descending, and finally harmonically with the interval ear trainer.
Watch the video below for a quick tutorial on how to use the guitar ear training software.