Err, I think I'd better clarify this as there might be a few people out there who would think that an F1 is still in medical school. There's no such thing as a "student doctor".
Foundation year doctors are newly qualified medical graduates who have to take a programme of training that lasts two years to obtain practical experience of being a doctor along with the competency involved. Most of the time, this training occurs in hospitals although some go directly to work in a GP practice. At the end of the first year, the doctor will become fully registered with the GMC. The doctor will then move on to the second year of Foundation Training, after which he/she will decide to specialise in a particular area of medicine.
An F1 doctor is equivalent to a House Officer under the old system and an F2 is equivalent to a Senior House Officer