How the roles of solicitor and barrister may overlap?

In the USA they'd just both be 'lawyers'. In more UK jurisdictions the 'lawyer' role is split. Barristers are the 'lawyer' who argue the cases in court, solicitor is the lawyer that does the office work on a case. There is of course overlap. Solicitors sometimes go to court (although they can't argue the case they could assist the barrister). The barrister often has to do some of the office and paperwork on a case besides going to court.