Whats the difference between two stroke and four stroke

How can I tell if an engine is a "two-cycle" or a "four-cycle" engine? Two-cycle engines use a mixture of oil & gasoline in a single fuel tank. Four-cycle engines do not require mixing of oil & gasoline and have separate gasoline and oil tanks.

More fuel efficiency :- 4 stroke engines have greater fuel efficiency than 2 stroke ones because fuel is consumed once every 4 strokes. Less pollution :- As power is generated once every 4 strokes & also as no oil or lubricant is added to the fuel; 4 stroke engine produces less pollution.