Soda crackers and saltine crackers are different names for the same food. In the United States, they are most commonly called saltines, while they are called soda crackers in the United Kingdom. Saltines are thin, crunchy crackers that are square-shaped with a perforated surface and salt sprinkled on top.
Saltines are made from white flour, baking soda, shortening and yeast. This gives them their characteristic dry texture when baked. The crackers are similar to hardtack, a dry biscuit cracker made from water, salt and flour. The main difference between saltines and hardtack is that saltines contain yeast, allowing their texture to be slightly lighter.