Particularly high in protein, durum wheat gives pasta the gluten it needs to hold its shape in boiling water. Fresh pasta absorbs more flavor from a sauce, but for my taste, its soft texture doesn't have enough character or body. I prefer the firmer texture of dried pasta for most recipes. Dried pasta is also more convenient, and it comes in an endless variety of shapes. Plenty of rapidly boiling water is the key to cooking pasta.
Pasta releases a lot of starch as it cooks.
If there isn't enough water in the pot, that starch will remain quite concentrated, making for some sticky pasta. Also, the vigorous action of a large amount of boiling water keeps the pasta moving around the pot so it cooks evenly and doesn't stick together. Many cooks add oil to the water thinking that it will prevent gummy pasta. This is not true. The oil simply floats on top of the water and has little effect on the pasta itself.