If it doesn't leap straight out at you, or you didn't notice from the post title, the image below is an e minor octave played on guitar. It's played on the thick strings of your guitar.
You may already know the notes of the e minor scale along your thick E string. If you don't know those notes along your D string you can learn them from this diagram. But, that's not entirely the point of today's lesson. We're looking at playing octaves. Give playing the diagram below a shot.
Question - when you played this did you hold the shapes and strum each octave? See, if you know tab correctly that's not what is tabbed above. The tab for that would also contain an X marker on the A string for each octave. To play this correctly you will need to use a hybrid picking and hit the D and E strings simultaneously. If you're a finger style player then no problem- you'll probably be using your thumb and finger of choice.