What is this white thing at the back of my throat?

This feels like a stupid question…but anyway, I was flossing my teeth earlier and looking really close in the mirror, when I swallow or just contract my throat it pushes up this very light pink/slightly white on the tip, firm structure (I don’t know how else to describe it) then it goes back down when I relax my throat again.

What is it? I’ve never noticed this before.