birota is an example of one way in which modern Latin handles concepts that the Romans had no word for. bi- is a prefix meaning consisting of, having, measuring, etc two of the things named.
Here are some cool examples from classical Latin; biceps two-headed, biclinium a dining-couch on which two persons can recline, bicodulus having two tails, bicornis two horned, bidens having two permanent teeth, biduum a period of two days, biennium a period of two years, bifer bearing fruit or flowers twice a year, biformatus (of a monster) consisting of two parts of different creatures, such as the minotaur, bigae a chariot drawn by two horses, bigarius, a driver of said chariot.
rota means wheel. Now, the Oxford Latin Dictionary has no entry for the word birota, but according to other (admittedly less reliable) sources it was used by the Romans to mean a two-wheeled cart, usually drawn by three mules, used for transporting commercial goods and one or two passengers. Which certainly makes sense. Today it is the generally agreed upon word for bicycle.
Riding a bicycle is a Passive activity in Latin. The Verb veho, vehere, vexi, vectum means to carry or convey. vehit means he, she or it carries or conveys. vehitur means he, she or it is carried or is conveyed. birota is in the Ablative Case and means by a bicycle.
Marcellus now at last walks straight to the bank. Do you see the young man who is riding a bicycle (literally, who is conveyed by a bicycle)? He is taking food someplace.