Renormalization is a mathematical and conceptual framework used primarily in quantum field theory (QFT) and statistical mechanics to address issues related to infinities that arise in the calculations of physical quantities. These infinities can occur in situations where interactions involve very short-distance (high-energy) processes. The goal of renormalization is to produce finite, physically meaningful predictions by systematically handling these infinities.
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The Biggest Ideas in the Universe | 11. Renormalization by Sean Carroll (2020)
Source. Gives a very quick and high level overview of renormalization. It is not enough to satisfy Ciro Santilli as usual for other Sean Carroll videos, but it goes some way.