A good analogy of the difference between a solicitor and a barrister is imagining the difference between a general practitioner of the medical profession and a surgeon.
Barristers are highly experienced officers of the court. In most family law matters, a private solicitor hired by a party will brief a barrister to represent as counsel for them and their client. A barrister will not ordinarily take instruction directly from a client, they will only take instruction from a solicitor.
Queen's Counsel are barristers of seniority and eminence who have been granted the title by the court.
Ordinarily, a barrister is not engaged by your solicitor until final trial, though they may consult with a barrister intermittently for advice and guidance on the matter.