The Marine Corps has three types of commissioned officers: Warrant Officers, Limited Duty Officers, and Unrestricted Line Officers.
Marine Corps Warrant Officers are technical specialists who perform duties that require extensive knowledge, training and experience with particular systems or equipment. Marine Corps Warrant Officers are selected from Marine Corps enlisted Noncommissioned Officers (NCOs) in the rank of at least E-5 (Sergeant), and must have at least eight years of enlisted service, and proven technical expertise in the equipment/procedures for the Military Occupational Specialty (MOS) they are selected for.
Like Warrant Officers, Limited Duty Officers (LDOs) are also technically oriented officers who perform duties that are limited to a specific MOSs. They require authority and responsibility greater than that normally expected of a Warrant Officer. LDOs wear the same rank insignia as do Unrestricted Line Officers. LDOs are selected from the Warrant Officer ranks. Selectees must have at least 8 years of Warrant Officer service, with not less than 10, nor more than 20 years of active duty service. LDOs are commissioned in the rank of Captain (O-3). Typically, you won't see very many general officer LDOs. Except in a very few cases, their promotion opportunities end at the rank of Lt Col (O-5), or Colonel (O-6).
Unrestricted Line Officers are the commissioned officers who can grow up to become Generals. They are primarily trained to command ground combat units or combat aviation units. In contrast to Limited Duty Officers and Warrant Officers, Unrestricted Line Officers are required to have at least a Bachelor's Degree, and they are not required to have previous military experience at the time of commission. They are commissioned through programs such as the Reserve Officer Training Corps (ROTC), the Naval Academy, the Marine Corps Platoon Leaders Course (PLC), and Marine Corps Officer Candidate Class (OCC).