In fact what we know as guinea pigs (Cavia porcellus officially) are originally from South America. They are rodents which have been domesticated and as such do not exist in the wild. They are believed to have originated from a closely related species Cavia tschudii. In their homelands they are kept for meat and also used in folk medicine and religious ceremonies.
That's not the case in Western countries, though, where they are mainly kept as pets - and delightful pets they make. They are docile, friendly and surprisingly intelligent for such small creatures. When my kids were young we shared our lives with Pam and Barbara - named by my young son after two family friends, who I suspect would not have appreciated the honour had they known - and for a short time, the only male, Guinea (apparently he was running out of inspiration at that point).
The two females could not have been more different in personality. Pam was small, short-haired and exceedingly busy all the time. Whenever anyone went into the yard she would bustle over to the fence around the run and chatter noisily. She loved to be stroked and enthusiastically explored whenever she was let out and never minded being picked up. Barbara was much bigger with a longer coat and did pretty much nothing. She ate, drank and lay in the sun. We nicknamed her the Brick in the end. She didn't object to being picked up but nor did she show any interest. Guinea was a cranky little creature who died suddenly from no obvious cause but he did leave a memento when Pam unexpectedly gave birth to a single baby which sadly also died within weeks.
Pam and Barbara were with us until they died of old age and Pam at least was very much missed.