On Earth, the sky appears blue during the day because sunlight interacts with our atmosphere, scattering shorter blue wavelengths of light in all directions.
Although there are billions of stars in the universe, they are incredibly far apart, and light from many of them hasn't yet reached us.
The human eye can only perceive light when it hits a surface or object and reflects into our eyes. In space, unless light from a star or another celestial body directly enters your eye, you won't "see" the light.
This paradox questions why the night sky isn't bright if there are infinite stars in the universe. The explanation is that the universe is finite in age and expanding. Since it's not infinitely old, there hasn't been enough time for the light from all the stars in the universe to reach us.
As the universe expands, the wavelengths of light from distant galaxies and stars are stretched, making the light shift towards the red end of the spectrum, or even beyond the visible range, into infrared or radio waves.