linear algebra – why does this equivalence hold $X-Ysucccurlyeq 0 iff begin{pmatrix}X & 1\1 & Y^{-1} end{pmatrix}succcurlyeq 0$

I’m struggeling to see that for two symmetric matrices $X,Y$ the following two conditions should be equivalent:

$$X-Ysucccurlyeq 0 iff begin{pmatrix}X & 1\1 & Y^{-1}
end{pmatrix}succcurlyeq 0$$

where $Xsucccurlyeq 0$ reads as $X$ being positive semi definite