From the Summary: " This report is designed to provide an overview of key reserve component personnel issues. The term 'Reserve Component' refers collectively to the seven individual reserve components of the Armed Forces: the Army National Guard of the United States, the Army Reserve, the Navy Reserve, the Marine Corps Reserve, the Air National Guard of the United States, the Air Force Reserve, and the Coast Guard Reserve. The purpose of these seven reserve components, as codified in law at 10 U.S.C. §10102, is to 'provide trained units and qualified persons available for active duty in the armed forces, in time of war or national emergency, and at such other times as the national security may require, to fill the needs of the armed forces whenever more units and persons are needed than are in the regular components.' [...] This report provides insight to reserve component personnel issues through a series of questions and answers that address  How reserve component personnel are organized (questions 2 and 4);  How many people are in each of the different categories of the reserve component (question 3);  How reserve component personnel have been and may be used (questions 1, 5, 6, 7, 9, and 11);  How reserve component personnel are compensated (questions 8 and 10);  The types of legal protections that exist for reserve component personnel (question 12); and  Recent changes in reserve component pay and benefits made by Congress (question 13)."
CRS Report for Congress, RL30802
Congressional Research Service: https://crsreports.congress.gov/