One of the oldest transitions on the books, famously favored by the Star Wars films (George Lucas deliberately revived the "scene-change grammar" of older cinema). A straight horizontal or vertical boundary is a basic wipe; a boundary that grows as a circle is an iris wipe; one that sweeps clockwise is a clock wipe.
It ships as a default preset in Premiere Pro's Video Transitions panel, and in After Effects you build it by hand — an animated mask over the second layer, which is really just an application of track matte.
Softening the boundary with a slight blur or gradient takes the edge off. A perfectly hard edge tends to read as dated, "old PowerPoint" territory.
When to use
Give the direction meaning — left-to-right could always mean 'next,' top-to-bottom 'a new section starts' — and stay consistent.