Stabilizers is a term that refers to hydrocolloid ingredients used at levels well under 1% (most often below 0.2%) to “stabilize” the body and texture of ice cream as close as possible to the desirable characteristics of the freshly hardened product.
They do this by controlling the behavior of water. Similar functionality can be found to lesser degrees in other ingredients used at higher levels, notably proteins and complex carbohydrates. Emulsifiers also stabilize body and texture by way of a different functionality.