It’s way too long and detailed to say anything about here, but the chapter on Semitic languages in The Unfolding of Language: An Evolutionary Tour of Mankind’s Greatest Invention, by Guy Deutscher is brilliant. It shows how those languages are constructed and how they evolved. He also puts it in the larger context of how other types of languages evolved. Highly recommended, but you do have to put in some work and pay attention. He makes it as simple as possible but there are inherently a lot of details to go through.
To give a one sentence summary, if pressed, Semitic languages are constructed around three letter roots. The various tenses and shades of meanings of related words are created by building on the roots in regular ways.
On preview, I see Poly has already given an explanation so I won’t go on.