The pentatonic scale is a 5-note scale that has been used in cultures all across the world. I like to talk about and use the major pentatonic scale. Let's assume you know your major scales (you know those, right?); the pentatonic scale is the major scale without the 4th or 7th scale step:
We can use the pentatonic scale as a source of melodic content as well as using it as a tool to get to our targets. I like to use them for both as each line we play should have the end-note (target) in mind. There is a seemingly endless supply of how you can use the pentatonic scale as melodic content, too. It's so powerful that the Temptations used it as one of the most recognizable phrases in music for the song My Girl:
Now you're singing it, right? See?! There's a strong melodic connection built in to the pentatonic scale. We can tap into that same content as a tool for our improvisations.
For this course, we will spend our time focusing on using them as a tool on the macro level (targeting the root, 3rd, 5th and 7th of the key), but I highly encourage you to find the most melodic ones that speak to you.