The major difference between the marines and the navy is their primary mission and area of operation. The United States Marine Corps (USMC) is a branch of the United States Armed Forces responsible for providing power projection from the sea. The primary mission of the USMC is to provide amphibious forces for the purpose of conducting land operations. The Marines also specialize in amphibious raids, counter-insurgency operations, and other operations that require specialized ground troops trained in amphibious warfare.
On the other hand, the United States Navy (USN) is the naval warfare service branch of the United States Armed Forces responsible for operations in the world’s oceans and seas. The USN’s primary mission is to maintain, train, and equip combat-ready naval forces capable of winning wars, deterring aggression, and maintaining freedom of the seas. The Navy also provides a wide range of humanitarian assistance and disaster relief operations, as well as environmental protection and security operations around the world.