What constitutes a robbery and an attempted robbery?

Robbery is the "felonious taking of personal property in the possession of another, from his person or immediate presence, and against his will, accomplished by means of force or fear." (Pen. Code, 211.) "The crime of attempt occurs when there is a specific intent to commit a crime and a direct but ineffectual act done towards its commission. ([Pen. Code,] 21a.) . . . . The act required must be more than mere preparation, it must show that the perpetrator is putting his or her plan into action. That act need not, however, be the last proximate or ultimate step toward commission of the crime. [Citation.]" (People v. Bonner (2000) 80 Cal.App.4th 759, 764.)

An aider and abettor acts with knowledge of the criminal purpose of the perpetrator, has the intent or purpose of committing or encouraging the offense, and by act or advice aids or encourages the commission of the crime. (People v. Beeman (1984) 35 Cal.3d 547, 561.)