Salt, nitrate, seasoning and sometimes sugar. Then it is left to air dry. Cheap bacon is soaked in a brine of salt, sugar, seasonings, sodium nitrate and other chemicals. I will eat the cheap wet cured bacon, but I will play close attention to the use by date.
Dry cure is more expensive, but IMO, a vastly superior product, and, I suspect, less harmful.
I appreciate that nitrates are not healthy but the press headlines do not seem to distinguish between wet and dry cured bacon.