Remote sensing is a way to get information about objects by collecting and analysing data without the instrument used to collect the data being in direct contact with the object.

For example, if you take a photograph of your house, and you see on the picture that the house is composed of a roof, walls and windows, all of which appear as different colours, this is remote sensing.

In Remote Sensing, three elements are essential.
These are:
1. a PLATFORM to hold the instrument
2. a target OBJECT to be observed
3. an instrument or SENSOR to observe the target

For example, when you take a photograph of your house, you are the platform, the photographic emulsion of the film inside the camera is the sensor and the house is the target.

A Key additional element (and the main purpose of remote-sensing systems) is:
4. the INFORMATION that is obtained from the acquired data and how it is used and stored.

In the example of the photograph of your house, the information obtained is all you can identify on the photograph about the house (for example: the colour of the shutters, a hole in the roof, an open window).  

For scientists, the platforms are all the means of being “at a distance” from the Earth’s surface (for example, planes and satellites). The target is our planet itself, the sensors are contained in all the instruments used to observe the Earth (cameras, scanners, radars, etc) and the information obtained in the end is everything that increases our knowledge about our planet (the cloud cover over Europe, the evolution of the ozone hole, the spreading of the deserts, the progress of deforestation, and much more).