What happened last time Trump imposed tariffs and how do they work?

U.S. President-elect Donald Trump has proposed implementing a tariff of 25 per cent on all goods imported from Canada on his first day in office.

What happened last time Trump imposed tariffs and how do they work?
U.S. President-elect Donald Trump has proposed implementing a tariff of 25 per cent on all goods imported from Canada on his first day in office.