Many students look into joining the military after high school. The U.S. Armed Forces – including the Army, Navy, Marines, Air Force and Coast Guard – allow young people to enlist after graduation anytime after turning 18.

Things to Consider Before Joining the Military 

What Are Your Interests?    
Joining the military will provide you with specialized training in any number of fields, depending upon the branch you are considering. Think about what skills you would like to possess at the end of your term of service. Learn as much as you can about each branch of military service and see which one will suit your needs.

What Skills Are You Bringing to the Table?
If you are already proficient with certain skills, perhaps you would like to hone these skills in the military. Whether it is working with computers, mechanics, or administrative duties, the military can provide you with the best training in a wide variety of areas.

Are You Willing to Make the Commitment?  
Many people are enchanted with the idea of the military, only to have “buyer’s remorse” after joining. Seriously contemplate whether or not you will be happy with the commitment you are going to make. Once you have enlisted, you are under contract with the US government, and getting out is no easy feat. 

Have You Been Fully Informed?
It is extremely important. You must ask all of the right questions before enlisting. Make sure you do the appropriate research and talk with as many people as possible. This way, you won’t feel misled or cheated when the actuality of your situation becomes evident. Don’t listen selectively; actively listen to your recruiter. Make a list of things you need to know about and get informed.

What Do You Want to Do in the Future?  
After being in the military for a while, some decide that they would like to make a career out of military life. Others decide that they would like to move on and pursue their education or a career in the civilian world with the skills they picked up while serving. Have your future in mind when selecting a job when you enlist.

One Last Thing to Consider:  Where Do You Want to Live?   
Look at the locations of the different services' bases around the United States and around the world. There are some beautiful locations these bases are located - and some not so nice.

Source: https://www.thebalancecareers.com

Overview

The President of the United States is the Commander in Chief, who is responsible for all final decisions. The Secretary of the Department of Defense (DoD) has control over the military and each branch - except the Coast Guard, which is under the Dept. of Homeland Security. With over 2 million civilian and military employees, the DoD is the world's largest "company."

Each branch of the military has a unique mission within the overall mission of U.S. security and peace. Here they are in a nutshell:

Air Force and Air Force Reserve:

The nation's source of air and space power. The primary mission of the USAF is to fly planes, helicopters, and satellites.
www.airforce.com  https://afreserve.com

Air National Guard:

The Air National Guard as we know it today is a separate reserve component of the United States Air Force.  https://goang.com/

Army and Army Reserve:

The dominant land power. The Army generally moves into an area, secures it, and instills order and values before it leaves. It also guards U.S. installations and properties throughout the world.
www.goarmy.com  

Army National Guard:

The Army National Guard is a group of soldiers who dedicate a portion of their time to serving their nation. Each state has its own Guard, as required by the Constitution; in fact, it is the only branch of the military whose existence is actually required by the Constitution.  www.nationalguard.com

Coast Guard and Coast Guard Reserve:

The Coast Guard's mission is primarily with domestic waterways. The Coast Guard does rescues, law enforcement, drug prevention, and clears waterways.
www.gocoastguard.com

Marine Corps and Marine Corps Reserve:

The Marine Corps is known as the U.S.' rapid-reaction force.' They are trained to fight by sea and land, and usually are the first "boots on the ground." Marines are known as the world's fiercest warriors.
www.marines.com

Navy and Navy Reserve:

The Navy accomplishes its missions primarily by sea, but also by air and land. It secures and protects the oceans around the world to create peace and stability, making the seas safe for travel and trade.
www.navy.com

Where are all these Military men and women stationed?

The U.S. operates in over 100 countries, including the U.K., Germany, Italy, Bahrain, Brazil, South Korea, Australia, Afghanistan, Iraq, and Japan just to name a few.

Source: https://www.military.com/join-armed-forces/us-military-overview.html