A sandwich spread is a liquid or paste-like dressing usually applied to the bread element of the sandwich. Sandwich spreads are intended to fulfill several functions:
Form a liquid-resistant barrier that prevents a moist filling from seeping into the bread and making it soggy.
Add moisture and a rich, smooth mouthfeel to sandwiches having less moist fillings.
Help the sandwich hold together by acting as a kind of glue, binding the bread, filling, and internal garnishes to one another.
Add a particular flavor or combination of flavors to the sandwich.
Add a particular color to the sandwich’s visual effect.