What the difference between laser and dot printer?

Dot matrix printers use a print head that builds the image with a series of dots on the page.  They have been obsolete since the 90s.  

Inkjet printers work by squirting tiny amounts of ink on the paper to form the page.  Biggest cost for an ink jet is the ink cartridges.  Plus the printers themselves will usually only last a few months.  They are cheaper and designed to be disposable.

Laser printers use a color toner that fused to the paper by heat/laser.  No ink is involved.  They give you a higher quality image that dot matrix or ink jet.  The printers themselves are more expensive but over the long run they are a lot cheaper to use.   

dot printers are now ancient and, afaik, no longer sold.  they use a series of pins striking a ribbon to transfer ink -- rather like an old fashioned typewriter did.  lasers use different technology -- electrostatic charge to attract the toner in only the 'right' places, which is then fused by heat to the paper

Mainly it's the quality of the image and the speed, and to a degree, how much it costs to operate each one.

A laser printer uses microscopically fine ink powder to print 1,200 dots per square inch, making a crisp image every time. A dot matrix printer uses pins that press an inked ribbon against the paper (in small dots, hence its name) and can achieve 240 dpi--but only by going over the area multiple times. Its best image is readable, but nowhere near as crisp.

Using black and white only for comparison purposes, a dot matrix printer in draft mode--one pass, no going back over characters to print them darker--may achieve 50 pages per minute, while a laser printer produces about 25 pages in much better resolution.

Dot matrix printers' pins make noise, a buzz or rattle, in operation. The laser is substantially quieter. Both have some noise as new sheets of paper are drawn from the paper tray. So how often you print and who the noise might bother could be factors.

The costs to purchase a mid-quality printer of either type are comparable. The cost of operation varies widely. Ribbons for dot matrix printers, while hard to find in stores, are inexpensive (and can be ordered online in anticipation of need). Ink cartridges for laser printer are far more expensive, and are a major factor in total cost of operation.

If your need is for printed pages that look professional to the recipient, I'd recommend a laser printer. If you will transmit pages digitally but want drafts you can mark up or share for input, a dot matrix might be fine.

A laser printer makes a high quality printed page like a book.  A dot matrix printer looks more like a type written page.  It's new vs old technology