A multi-tool is, just as the name implies, a taal that can be used for multiple purposes. There are oscillating multi-tools and rotating multi-tools. A oscillating multi-tools lets your - as long as you're using the correct accessories - saw, scrape, sand, and grind. Think of sawing cutouts, scraping off glue remnants, or cutting through baseboards. You can use a rotating multi-tool for more detailed jobs, such as engraving, sanding small surfaces, or woodworking.