Guide
Egg vs semolina: the two doughs
Almost every pasta is one of two recipes. The dough tells you the region, the texture, and the sauce.
Strip away the hundreds of shapes and nearly all of Italian pasta comes down to two doughs. Knowing which one you are holding tells you where it comes from, how it will feel, and what it wants on top.
Semolina and water
Coarse-ground durum wheat semolina, mixed with water and nothing else, is the dough of the South and of dried pasta. Durum is hard and high in protein, so it holds a firm bite, and it is the wheat that survives drying without turning brittle. This is spaghetti, penne, rigatoni, the extruded shapes that fill the supermarket aisle, built for tomato, oil, and seafood.
Soft wheat and egg
Finer soft wheat flour bound with egg is the dough of the North, of Emilia-Romagna's sfoglia rolled by hand. The egg makes it rich, golden, tender, and a little porous, so fat clings to it. This is tagliatelle, tagliolini, the filled tortellini and ravioli, made for butter, cream, and gentle ragus.
Where they cross
The line is not absolute. Some hand-formed Southern shapes use semolina worked by hand without egg, like Puglia's orecchiette, and a few Northern cuts add egg to a semolina base. But as a first guess, egg means North, fresh, and tender; semolina means South, dried, and firm. The dough is the quiet fact under every shape.