The concept you're referring to is one of the fundamental principles in physics known as the theory of relativity, specifically the theory of special relativity developed by Albert Einstein. According to this theory, the speed of light in a vacuum, denoted by 'c', is considered to be a universal constant that cannot be exceeded by any material object with mass.
The theory of special relativity introduces the concept of relativistic mass, which increases as an object's velocity approaches the speed of light. As an object with mass approaches the speed of light, its relativistic mass becomes infinitely large. At the speed of light, the relativistic mass would theoretically become infinite, meaning that an infinite amount of energy would be required to accelerate the object further.
This phenomenon is often explained through the concept of time dilation and length contraction. As an object's velocity increases, time dilation occurs, meaning that time appears to slow down for the moving object relative to a stationary observer. Additionally, length contraction occurs, where the length of the moving object appears to shorten in the direction of motion as observed by a stationary observer. These effects become more significant as the object's velocity approaches the speed of light.
As a result, it would require an infinite amount of energy to accelerate an object with mass to the speed of light, which is why it is considered impossible according to our current understanding of physics. However, it is important to note that particles without mass, such as photons (particles of light), travel at the speed of light in a vacuum.