No. Bún is just the word for vermicelli noodles in Vietnamese (rounded noodles). Thịt means meat, nướng means grilled. Chả can be made of meat or fish but basically it’s chopped into tiny pieces and molded into a shape. Bún is used in a lot of viet dishes (like the well known bún bò Huế - which is vermicelli noodles with beef from the region of Hue, as the name indicates). It’s the difference in meat, broth, and fish sauce that really sets them apart. Bún thịt nướng usually also has an egg roll in it too.