Button up, collared shirt. “Dress Shirt”. Oxfords are different because they’re woven rather than shiny. So a little more reasonable to wear with jeans
Kinda like how a sport coat (which is what I actually have, and not blazers) is different from a suit jacket. An Oxford doesn’t have the very dressy collars or cuffs or the very dressy shine.
Also, I said slacks but I’m actually wearing chinos. Again, because you can wear those to a backyard Barbeque. They aren’t really dress pants. No pleats or anything.
All of that, again, is born from being a cheapskate and wanting to maximize the versatility of a clothing item. Can I “get away with” wearing these things together in a business meeting but then also separately to the bowling alley with my kids. Haha.