This is an excerpt from an Adobe document which should apply to Premiere Elements in general
The Snap option, which is enabled by default, makes it easier to align clips with each other or with particular points in time. You can move a clip with the Snap option selected. The clip automatically aligns with the edge of another clip, a marker, the start and end of the time ruler, or the current‑time indicator.
Snapping also helps ensure that you don’t inadvertently perform an insert or overlay edit when dragging. As you drag clips, a pop‑up window displays the distance, in frames, that you have moved them. A negative number indicates you’ve moved them toward the beginning of the movie.
Choose Timeline > Snap. A check mark indicates that the option is enabled