Unmanned aerial vehicles (UAVs), or drones, are crewless aircraft that are controlled:

Remotely (e.g., from the ground or another aircraft);
by means of autonomous software installed onboard the UAV;
by means of GPS navigation.

UAVs have a frame made of light composite materials or light metal alloys to which other elements are attached:

A flight controller that receives signals from the ground control panel or on-board computer and redirects them to other elements of the structure. The basic set of controller elements includes:
sensors for altitude (barometer) and position in space (gyroscope),
device for measuring acceleration (accelerometer),
GPS navigator, Wi-Fi, RAM;
motors, propellers and speed controllers that ensure the flight;
batteries.

There are 4 main types of drones by variety of design:

01 – multirotor – multicopter drones are the most common type. They are flying platforms with 3, 4, 6, 8, 12 brushless motors with propellers. In flight, they keep their horizontal position relative to the ground and can hover over a certain place, move sideways, forward, backward, up and down, rotate around their axis. Actions are performed by changing the thrust on each motor;
02 – Fixed-wing UAVs – drones that use a “wing” to fly and generate lift, just like conventional airplanes. They cannot hover in place in the air, fighting gravity, but can move forward on a set course as long as their power source allows. They are most often piloted by the pilot on board the aircraft, but some are designed to be remotely controlled or controlled by a computer;
03 – single-rotor drones – unmanned helicopters – UAVs similar in design to real helicopters. Unlike a multi-rotor drone, they have 1 large lead rotor and a small tail rotor for course control. More efficient than multi-rotor: they have higher flight time and can be powered by internal combustion engines. But due to their more complex design, they have high cost and operating costs;
04 – Hybrid drones are unmanned aerial vehicles that combine the advantages of fixed-wing models (e.g., higher flight time) with the advantages of propeller-based models (e.g., the ability to hover). Hybrid aircraft designs have been designed since the 1960s, but were not very successful at the time. However, with the advent of a new generation of sensors (gyroscopes and accelerometers), hybrid design gained new life and direction.

Nowadays, UAVs are actively used in a wide variety of industries:

in architecture and urban planning a system using a drone and special software can autonomously survey the terrain and form 2D and 3D maps and models of the area;
in urban areas, UAVs can search for unauthorized dumps, detect illegal buildings, control the quality of road surfaces, take air samples, etc;
in cartography and cadastre, drones help to obtain orthophotomaps for mapping, cadastre registration, etc;
in photography and cinematography, UAVs help to take professional photos and videos;
in agriculture, drones are capable of detecting arid areas, gaps, crop failures, and can also be used for spot spraying of plants and fruit trees.

The oil and gas industry also benefits from the use of drone technology solutions:

allow for preliminary analysis of prospective subsurface areas,
carry out geodetic surveying for design and preparation of seismic surveys
monitor pipelines for leak detection
detect the condition of construction sites, etc.