The concept you're referring to is known as "cosmic light travel distance" or "observable universe." It's true that the age of the universe is estimated to be around 13.8 billion years old, and you might wonder how we can observe light from objects that are further away than the age of the universe itself. The key to understanding this apparent discrepancy lies in the expansion of the universe.
The universe has been expanding since the Big Bang, and as it expands, the fabric of space itself stretches. This expansion affects the wavelength of light traveling through space, causing it to stretch as well. This phenomenon is known as cosmological redshift.
The cosmological redshift means that light emitted by distant objects gets "stretched" as the universe expands, causing its wavelength to become longer, and therefore, its color to shift towards the red end of the spectrum. This redshift is proportional to the distance between the observer and the source of light.
When astronomers observe light from very distant objects, such as galaxies billions of light-years away, they are essentially observing that light as it was emitted billions of years ago. The light from these distant objects has traveled through space for billions of years to reach us, and during that time, the universe has been expanding, causing the light to redshift.
So, when scientists detect light from objects that are, say, 46 billion light-years away, they are seeing the light that was emitted when the universe was much younger, even though the objects themselves are now much farther away due to the expansion of space. This allows us to study the early universe and gain insights into its history, despite the seeming contradiction with the age of the universe.