What is McKenzie Friend?

Legal Definition
A McKenzie friend assists a litigant in person in a court of law in England and Wales. This person does not need to be legally qualified. The crucial point is that litigants in person are entitled to have assistance, lay or professional, unless there are exceptional circumstances.

Their role was set out most clearly in the eponymous 1970 case McKenzie v McKenzie. Although in many cases a McKenzie friend may be an actual friend, it is often somebody with knowledge of the area, and the trend is heavily in favour of admitting McKenzie friends. He or she may be liable for any misleading advice given to the litigant in person but is not covered by professional indemnity insurance.

The role is distinct from that of a next friend or of an amicus curiae.
-- Wikipedia