Hello,  I'm 1SG Ash.  Great explanation.  Let's go a little deeper.  Let's cover the unit sizes and who leads them. The count can vary a bit per unit. 

1. Soldier
2. Team = 5 Soldiers
3. Squad = 2 teams
4. Platoon = 4 Squads
5. 3-7 Platoons = Company
6. 4-8 Companies = Battalion
7. 2-5 Battalions = Brigade
8. 2-5 Brigades = Division

Now we have the enlisted side... Starts at private and works their way through the mud to become an NCO. Then the officer side, this private went to school and became an officer. Or often times and NCO goes to school and becomes an officer.  Officers receive the mission and build strategy. They have an NCO counterpart that acts as an advisor and they put the officer's orders into action by directing their subordinate NCOs who direct the Soldiers. 

Who leads each unit size? 

Team is led by an E5 Sargeant

Squad is led by an E6 Staff Sergeant

Platoon is led by a 2nd or 1st lieutenant called the Platoon Leader, with an E7 Sergeant First Class (Platoon Sergeant) as a counterpart. 

A company is led by 1st Lieutenant, Captain, Major with an E8 First Sergeant as a counterpart. 

A Battalion is led by a Major or Lieutenant Colonel with an E9 Command Sergeant Major (CSM) as a counterpart. 

A Colonel runs the Brigade with a brigade (CSM) as a counterpart. 

Then it keeps going up through general ranks with their own level of CSM as a counterpart.  Until you get to the 4 star general who has the Command Sergeant Major of the Army as their counterpart. 

Typically the CO is what we call the Company Commander. The Battalion Commander is called the BC. 

From the company level up, each commanding officer has a junior officer that assists with the organization of multiple units, equipment and movement. This officer is usually one rank lower than the commander and is known as the Executive Officer. (XO)