Not only leaflets
Printing is not only printing leaflets, business cards or large banners - it also prints other, necessary materials such as: stickers, self-adhesive letters or labels. In principle, everything that comes out of the printing house can be included in the category of printing.
There are plants specializing in the production of only a specific group of printed materials: eg leaflets, or only large-format printing. However, this results from a simple thing: for every type of printing you need to have the right machine, and these take up space and cost a lot. That is why printing plants limit the amount of services provided.
Laser printing in Wikipedia
Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively charged cylinder called a "drum" to define a differentially charged image.1 The drum then selectively collects electrically charged powdered ink (toner), and transfers the image to paper, which is then heated in order to permanently fuse the text, imagery, or both. As with digital photocopiers, laser printers employ a xerographic printing process. However, laser printing differs from analog photocopiers in that the image is produced by the direct scanning of the medium across the printer's photoreceptor. This enables laser printing to copy images more quickly than most photocopiers.
Źródło: https://en.wikipedia.org/wiki/Laser_printing
Offset printing - types and types
Offset printing is the most popular type of printing in today's printing industry. It is true that it has many varieties and uses different techniques and materials (paint, paper). The main division is cold printing, where the paint is fixed by soaking into paper. While the 'hot' offset where the printed paper web passes through the drying tunnel.
The classic offset (water) is associated with the use of water rollers and hydrophilic and hydrophobic surfaces, however, this method is already abandoned due to the difficulty in obtaining a good balance of water and oil paint.
The successor of this method is anhydrous offset printing where silicone molds are used instead of water.