Question about progesterone

So my doctor just prescribed me progesterone suppository as I am doing <a href="https://glowing.com/glow-fertility-program">IVF</a>.

My question is...

Does this mean that even if I was not doing <a href="https://glowing.com/glow-fertility-program">IVF</a> my progesterone levels would be low or is it only for people who do <a href="https://glowing.com/glow-fertility-program">ivf</a> and why is that??

Can someone please explain to me.