The stars visible to the naked eye ... those with "visual magnitudes" of
roughly 6 or lower ... total about 5,000 or 6,000.
When you introduce optical aid ... telescopes etc. ... the number
immediately becomes uncountable.
-- The part of our own galaxy ... the "Milky Way" ... that we can see
and photograph, leads us to estimate that there are a total of 200
to 400 billion stars, in our own galaxy alone.
-- The number of galaxies we see on various photographic images
leads us to estimate the number of galaxies in the observable universe
at something like 100 to 300 billion galaxies. But a recent German
supercomputer simulation put that number nearer to 500 billion galaxies.
In other words, there could be a galaxy out there for every
star in the
Milky Way, and billions of stars in every one of them !
Now you do the math. And remember, we're only talking about the
observable universe. We don't see any end to it, and we don't have
light-gathering monsters to see any farther than that, so there's even
more to it.