The Royal Naval Reserve are a part of the Royal Navy of the United Kingdom.
Background
Impressment
As the Royal Navy came to its more modern organisation during the 17th century it adopted the practice of impressment to provide the bulk of the crews.
The process of impressment was not suitable for the recruiting of officers, and the procedure adopted there was that officers received a basic pay for their rank when they were holding an appointment and half of that when between appointments (half-pay). Officers in command of ships or establishments received additional 'Command money' which varied with the status of the ship or establishment involved.
'Prize' scheme
Officers and men also received extra payments under the 'Prize' scheme. While this could arise in several different ways the most common by far was the capture of an enemy ship and its subsequent purchase by the Navy (a feasible process with wooden ships). For the ordinary sailor the amount was typically a few shillings (although this represented several months pay) but for the commanding officer it typically amounted to hundreds of pounds. Thus many captains had estates ashore which gave them an alternative income.
Junior officers were in a much more parlous state, as it was not really possible to keep a home on the half pay for a Lieutenant. This was part of the reason why marriage by junior officers was so frowned upon.
Volunteering campaigns
Impressment was eventually dropped in the early part of the 19th century in a move to encourage seamen to volunteer for full career employment in the naval service. This was fine for the numbers required during peacetime when many vessels were laid up in reserve but it meant that some means had to be provided to produce the extra men needed when the fleet expanded in time of war. An Act of Parliament of 1835 had established The Register of Seamen to identify men for naval service in the event of war, but in 1854 just 400 volunteered for duty out of 250,000 on the Register. The Register of Seamen was supplemented in 1853 with the creation of the Royal Naval Coast Volunteers (RNCV) comprising boatmen and fishermen who would undertake limited (geographic) service in the Navy during a conflict. This meant the Baltic fleet of Admiral Charles Napier was seriously undermanned for the blockade of Russia's Baltic ports during the Crimean War, and as an MP Napier campaigned for improvements in the treatment of sailors.