In order to become a good improviser, you need to understand what you are playing and be able to transfer anything you hear from your mind to the fretboard. To do this, you need a system for identifying pitches which can apply to any scale in any key. Scale degrees identify a note's position in the scale in relation to the root note or keynote (the note after which the key is named - also called the tonic).
Here are the notes of the C major scale with their scale degrees. Try playing the scale and singing the scale degrees as you play. It is important to learn scale degrees well because they are essential for transposing music to other keys, and for playing effectively over chord progressions.