The Italian word Pasta has many meanings, including "pastry", "dough", "pastry" as in "small cake", or "paste". In English, the word is generally understood to mean certain types of noodles that are produced from the paste of ground grains mixed with water, and often egg and salt.
Wheat noodles are by far the most common noodles in Asia (c.f., Japaneseudon and somen) and Europe (c.f., spaghetti), while rice noodles tend to be rare outside of Asia. In English-speaking countries, Italian noodles are the kind most often referred to as "pasta". In Italy, spaghetti with tomato sauce (sugo) and Parmigiano are usually referred to as "pastasciutta" ("asciutto" means "dry" or "dried").
While it has been thought in some places that Marco Polo brought the concept back with him from China (from where should come spaghetti), the first pastas that we know about in Europe were on Etruscan tombs from the 4th century BC.