As the dramatis personae at the beginning of the text indicates, there are five characters seen on stage in Waiting for Godot.
Vladimir and Estragon are two clowns (in the colloquial sense of the word). They spend their days in idle banter waiting for a mysterious Godot -- who neither man has ever actually met or seen, but whom both (at times) are convinced will be arriving at the tree on the corner of a road where they currently reside.
Midway through the first act, a loudmouthed slave-driver named Pozzo arrives. Didi and Gogo mistakenly believe Pozzo to be Godot, but he soon assures them in no uncertain terms that this is not the case. In the second act, Pozzo returns and appears to have suffered a strange twist of fate.
Pozzo is flanked by Lucky, an elderly bag-carrier who appears at first to be deaf-mute and almost subhuman. Pozzo swears that Lucky taught him everything he knows, which confuses Didi and Gogo, and Lucky later launches into a nonsensical monologue, which only serves to further confuse the two travelers.
The final character who appears onstage is "the boy," an apparent messenger from Godot himself. The boy brings news to the men from the unseen Godot. Like Pozzo and Lucky, the boy appears once in each act of the play.
Godot is never seen onstage. His identity remains largely a mystery, both to the characters and to the audience. Some have suggested that the etymology of the character's name indicates that he is, in fact, a "God"(ot) -- while others have argued that the character is merely symbolic of an eternity spent waiting for any unseen reward. From the characters perspective, Godot has sent for them (or so they believe), and has promised to arrive at this predestined spot at this predestined time (but again, they are increasingly unsure of the validity of this information as the play unfolds).