nLab
frame of opens

Given a topological space $X$, the open subspaces of $X$ form a poset which is in fact a frame. This is the frame of open subspaces of $X$. When thought of as a locale, this is the topological locale $\Omega (X)$. When thought of as a category, this is the category of open subsets of $X$.

Similarly, given a locale $X$, the open subspaces of $X$ form a poset which is in fact a frame. This is the frame of open subspaces of $X$. When thought of as a locale, this is simply $X$ all over again. When thought of as a category, this is a site whose topos of sheaves is a localic topos.