What is the difference between arrabiata sauce and marinara sauce?

Marinara is a smooth basic tomato sauce. Arrabiata sauce typically includes red pepper flakes, which makes it spicier.

Marinara is your traditional tomato sauce used on pasta. Arrabiata is spicier tomato sauce made from tomatoes, garlic, and red chili peppers which is cooked in olive oil.  The chili peppers are what give it the heat.  Arrabbiata sauce is usually served with penne pasta.

Marinara sauce is a quick sauce, seasoned only with garlic, crushed red pepper, and basil. It is best when made with whole San Marzano or plum tomatoes, coarsely crushed by hand or passed through a food mill. Marinara can be left chunky; the texture of the finished sauce is fairly loose, and the taste is that of fresh tomatoes.