Dry toner is melted onto paper by the Fuser. A dusty black powder on a freshly printed piece of paper is likely an issue with the Fuser failing to melt the toner onto the page. Without this step the toner will move around and spread causing the dusty appearance. The fuser may need to be replaced or it's settings adjusted for the type of paper (e.g. some specialty paper may need a higher temperature - consult the printer's documentation to see if this is possible).
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. The drum then selectively collects electrically-charged powdered ink (toner), and transfers the image to paper, which is then heated to permanently fuse the text, imagery, or both, to the paper. As with digital photocopiers, laser printers employ a xerographic printing process. Laser printing differs from traditional xerography as implemented in analog photocopiers in that in the latter, the image is formed by reflecting light off an existing document onto the exposed drum.
Invented at Xerox PARC in the 1970s, laser printers were introduced for the office and then home markets in subsequent years by IBM, Canon, Xerox, Apple, Hewlett-Packard and many others. Over the decades, quality and speed have increased as prices have decreased, and the once cutting-edge printing devices are now ubiquitous.