What is the thing called that has a dot and comma under it?

You're likely describing the cedilla, a diacritical mark used in the Latin alphabet. It looks like a comma placed under a letter, most commonly the letter "c".

The cedilla is used in several languages, including:

* French: It changes the pronunciation of "c" before "a", "o", and "u" from /k/ to /s/. For example, "ça" (pronounced "sa").

* Portuguese: It modifies the "c" to a /s/ sound before "a", "o", and "u" in some words. For example, "ação" (pronounced "ah-sawn").

* Turkish: It modifies the "c" to a /dʒ/ sound. For example, "çift" (pronounced "chift").

Let me know if you had something else in mind!