Apaixonado translates to "in love" or "smitten". While the root word "paixão" (passion) is common, apaixonado is a more specific and evocative adjective that perfectly captures the song's central theme.
In the lyrics, the singer describes himself as "Um bobo apaixonado" (a smitten fool), highlighting his intense, almost foolish, adoration for the person he's watching. It's a key word that conveys the depth of his romantic feelings and sets the tone for the entire song.
"Sabe Quem Eu Sou" is a shy love song told from the point of view of an admirer who never works up the nerve to speak. Every day the same woman walks down his street, and every day he just watches from a distance, wondering if she has any idea who he is.
The repeated question "Sabe quem eu sou?" ("Do you know who I am?") is the heart of the song. He answers it himself: he's the guy on the other side of the street, quietly counting the minutes until he sees her pass by again. It's a simple, gentle picture of a crush that never quite becomes a conversation.