Marine Corps is the national defense forces assigned for naval combat, defense or protection through the water. Back in the day, marines undertook these tasks, helping to maintain peace and order in the ship as there is a risk of mutiny, capturing ships and vessels, during and after combat, and supplying the manpower to raid to fulfill naval objectives. After industrialization, in the 20th century, the number of land operations increased, which led the marine forces to evolve and specialize skills of amphibious warfare. They are different from the Navy because the Navy controls the entry and exit points of seaports whereas, Marines are used mainly for amphibious combats, which means both land and water combats.
Navy mostly supports the air force and vice versa, when it is needed. On the other hand, Marines support the army when superfast deployment is needed. And the most important reason is, the Navy is totally independent but, Marine Corps sometimes depend on the Navy for support in administration and logistics. In some countries, the Marine Corps is a department in the Navy and in the other countries, they are not a department under navy but, not totally independent as they use their support from the Navy.