I also drag straight to the timeline….
Insert: When you drag your clip to the timeline your mouse pointer becomes an arrow pointing to the right and signals an insert edit.
Overwrite: When you drag your clip to the timeline your mouse pointer becomes an arrow pointing down to signal a overwrite edit.
Just a couple FYI’s for you insert/overwrite is the most basic of any editing program and they aren’t the terms I call them they are in fact the technical terms used in all editing programs also no offense at all to you but I would imagine googleing this question or checking out the manual would be faster then posting in a forum and waiting for answer.
But anyway hope I helped. Happy editing.