What is "Orb Walking"?

It was a term used in another MOBA, DOTA.

Some ranged heroes had abilities that could be toggled on/off and would modify their auto attacks. People found out that instead of toggling the ability, you could manually cast the ability each auto attack. This was significant because the attack would be classified as a spell rather than an auto attack (that was being modified) and thus not cause minion aggro (would only target and attack you if you auto attacked a hero, but not if you cast a spell). Additionally, you could cancel your champions wind-down animation and force your hero to move early with a move command (where they otherwise would have stood still and completed their wind-down animation). By canceling this animation, you were able to move earlier then normal (and thus run more distance than you normally would).

In essence, you were manually casting each auto attack as an ability, forcing your hero to move and skip unnecessary animations, and repeating.

This term carried into LOL, as the second half (canceling attack animation to move earlier) can be done.

Another word for kiting, moving between auto attacks

Wasn't it a Ryze strategy, where when only and your lane opponent are left, you cast E to bounce off from the enemy then to you then back to the enemy, simply to increase damage output.

Her passive is orb walking made easy.

orb walking is just canceling your aa animation right as soon as you can so the projectile still goes out and does damage so you can keep attacking... Literally that's all it is. you need 1.4 attack speed to do it effectively other wise you have to cancel your aa's before your projectile goes out for damage.. still useful below 1.4 AS for dodging harass in lane ... It's worth to cancel your aas early and miss 1 cs to dodge like say brand W..

after 1.4 AS you can keep on someone while you attack. Kiting isnt efficient below that attack speed unless you have some kind of gap creator like Ez E or flash or heal to kite with; you cant finish your aa animations and still move back in time to escape their damage.

AKA: Attack-Move and Stutter Stepping, Orb Walking is the canceling of the latter, and unnecessary, part of your AA animation with movement commands to benefit your mobility.

It is mandatory to learn, especially for the ADC role. It is less useful for melee (and Thresh) than ranged, but it still produces negligibly improved mobility when done right.