is "inside" and "outside". Diz and Bird soloed more outside of the structure, and it was the want to get outside of the confines of a tune's structure that gave birth to be bop. If you get a book of Bird's transcribed solos, you'll see what I mean, especially if you get a book of Armstrong's solos. As good as Satch was, he stayed within the structure of the tune, for the most part.
A lot of what D & B did was based upon motif, chord substitution (especially tri tone), and displacement. A very simple example would be to take a 4 note arpeggio, and begin it on the tri tone sub, then repeat it- move it up chromatically until you hit a chordal note of the next chord, or maybe one that is a few measures away.
Let me see if I can describe this: begin with a basic circle 6- I / vi / ii / V7, one chord per measure, in the Key of C. For description's sake, let's limit to 16th notes. So we start with the I chord- it's tri tone is F#. We'll use a basic dominant 7th chord here, in root position- 1, 3, 5 b7. Begin it on the tri tone- F#, play it once, beginning on the second 16th of beat 1, then move it up a half step, then repeat it on G, then on G#, then A. Now you see that you have stopped on a G, one 16th note before the second measure of the progression, which is an A minor. Hold the G which is now the dom7 of A, over into beat 2 of the A minor, then play a B on beat 3 and a D on beat 4- a simple G triad. Hold the D in the next chord, and it becomes the tonic of the ii, a D minor. But we are going to make it a D major, and play an F# against it, which is, of course, the tonic of the F#7 we started of with. Play the F#7 on beat 2 of the D minor, and repeat it in an ascending cycle of 4ths- F#, B, E, A You last note will be G which will land you on the tonic of the V7 chord, the G. On beat 3 play a Bb, and hold it until the C of the progression comes around again, then play it's lower tri tone, which is an E, the third of the C Chord.
I hope this makes sense- it's much easier to play than describe. And one more thing- experiment with ignoring chords between your target notes. Like in this example, look at it like one big 4 measure C chord, and play a mode on the C. Noodle on an F7 for 4 measures and see if you like that sound.
Granted no Jazz player would play it this simply, but this is a beginning point, and it will help you to train your ears and think in terms of target notes- picking a note from one chord, then another from one a few measures away- and how to get from one target note to the next. When you can think like this, then you can pick your target notes from non chordal tones, construct you own melody between your target notes, etc., and solo away.
I prefer the target note way of soloing, because I have found I can construct more interesting melodies that way. In my opinion, focusing on playing modes will result in what a jazz friend of mine calls the "whee doobies" a solo that goes "Whee, doobie, doobie, doobie", and makes no sense at all, except to be a chance to play a bunch of modes and show off chops. But a lot of players were brought up on playing modes, so YMMV. Whatever works for you.
My opinion of Diz and Bird is that they were brilliant mathematicians as well as musicians, becasue it takes a lot of brain work to figure this Be bop theory stuff out, much less play it/