Impressment (the Press) was the act of forcing men to serve in the navy. The people who were "pressed" to join the navy were usually young men. A naval officer would lead a press gang and force men onto warships where they were made to serve as sailors. Their families (if they had families) seldom knew where they had been taken.
This was a normal practice in the Royal Navy during the 17th, 18th and early 19th centuries. Many people said that it should be stopped, but the Navy said it was a good way to get sailors who were needed to defend their country. After the Napoleonic Wars the need for sailors was less and the Navy stopped impressing them.