Explainer videos are defined more by their purpose (to explain ideas, systems, business models) than any animation style.  This said, explainer videos have become increasingly the go to animations for corporates and small to medium businesses alike.  Their simple stylized look and feel helps the viewer focus on what’s important without too many distractions.  This style is sometimes accompanied by infographics, icons and attractive transitions and can be tailored to work with your current branding.