Mobile Task Force is an elite group of highly-trained personnel, specialized in various duties and accomplishing specified goals, Mobile Task Force deploys in emergency situations and has 3 sub-divisions, each specializing in their prioritized goal.

Mobile Task Force Alpha-1 is an unknown type of MTF, all information regarding the unit is highly classified, however, it should be known that the method of joining it is strictly handpicked from MTF. They also specialize in VIP protection and all other MTF's duty execution.

In-game, Alpha-1 gets a dark grey colored uniform with a pair of Night Vision Goggles. Alpha-1 is the only team that gets Night Vision Goggles in-game, their hierarchy as follows:
Handpick.
Probationary Agent (Level-4);

Operative (Facilities Senior Staff);

Supervisory Special Agent (Facilities Senior Staff);

Operator-in-Charge (Deputy Commander, Facilities Senior Staff);

Commander-in-Charge (Commander, Facilities Senior Staff);

Assistant-Director of Task Forces (Site Command).

Mobile Task Force Nu-7 is one of the Specialized MTFs (SMTFs) which deals with Chaos Insurgency raids (3 CI+) and SCPs re-containment, under Epsilon-11's jurisdiction.
Nu-7 holds the jurisdiction during Riot Events and Chaos Insurgency raids.

Nu-7 gets M240 in-game, a  sub-machine gun armed with huge amount of bullets, as well as stamina-boost and health-boost.
MTF Academy.
Recruit (Level-1);

Trainee (Level-1);

Probationary Operative (Level-2);

Private (Level-2);

Specialist (Level-2);
Field Sergeant (Level-3);
Field Lieutenant (Level-4);

First Lieutenant (Deputy Commander, Level-4);
Field Captain (Commander, Level-4).
Nu-7 additionally may use a white camo, allowing them to be less visible.

Mobile Task Force E-11 is one of the specialized Mobile Task Forces (SMTFs), which specializes primarily in SCP Containment Breaches, those being: SCP-106, SCP-049, SCP-096, SCP-008 - only during mass infections. E-11 as Nu-7 gets boosts in-game, those being health boost and small stamina boost. Epsilon-11 also deals with 3+ CI raids, mandatorily during 5+ CI raids.

E-11 First Lieutenants as well as Captains with Nu-7 get a special uniform variation which has a beret, their hierarchy as follows:
MTF Academy.

Recruit (Level-1);

Trainee (Level-1);

Probationary Operative (Level-2);

Operative (Level-2);

Agent (Level-2);
Field Sergeant (Level-3);
Field Lieutenant (Level-4);

First Lieutenant (Deputy Commander, Level-4);
Field Captain (Commander, Level-4).

R&E is the main department that specializes in SCPs researching, usually having a main goal of testing on them, but they also conduct other sessions / activities, those being: Maintenance & Inspection; Physiological Assessment; Cleaning Sessions; Interviews and External Operations.

R&E Junior Researchers get L-4 and a radio instantly when they spawn, Senior Research Staff gets L-5 and Encrypted radio channel access once deployed. (Note: Senior Research Staff uniform is broken)
Applications.

Intern (Level 1);

Junior Researcher (Level 1);

Associate Researcher (Level 2);

Researcher (Level 2 / Level 3);

Senior Research Staff (Level 3);

Scientific Board (Level 4);

Research Coordinator (Level 4);

Head of Research (Second-in-Command - Facilities Senior Staff);

Assistant Director of Research (First-in-Command - Site Command).

Internal Tribunal Department deals with Internal Cases, such as reports on official staff and other information upholding. Internal Tribunal Department also gives punishments personnel and originally is Ethics Committee.

Internal Tribunal Department doesn't get an in-game uniform nor a team, however, they're allowed to enter Site Command Offices, their hierarchy as follows:
Applications.

Department Advisory Council (N/A);
Tribunal Paralegal (Level 1);

Tribunal Junior Attorney (Level 2);

Tribunal Attorney (Level 2);

Tribunal Senior Attorney (Level 3);

Tribunal Magistrate (Level 4);

Attorney-General (Second-in-Command - Facilities Senior Staff);

Assistant-Director of Justice (First-in-Command - Site Command).
ITD staff usually deploy on the Ethics Committee department in-game.

Internal Tribunal Security Administration is one of the most classified departments within Site-19, being a replacement for Department of Analytics and managing all personnel's data, such as their punishments background and surveillance. (ENTRY METHOD IS STRICTLY HANDPICK, ITD PERSONNEL DO NOT GAIN MORE CHANCES TO JOIN.)

Internal Tribunal Security Administration use the Department of Analytics team on-site and personnel below Senior Field Analyst use alternative accounts, such as Agent_TH. (Information regarding that is unconfirmed and is more of a theory)
Handpick.

Junior Analyst (Level 2);

Field Analyst (Level 2);

Senior Field Analyst (Level 3);
Department Superintendent (Level 4);

Chief Analytics Officer (Second-in-Command - Facilities Senior Staff);

Assistant Director of Analytics (First-in-Command - Site Command).

These are not every department Site-19 offers, for more information review Foundation Overview and for uniforms, Foundation Regulations.