Slightly dumb question, but when writing a SQL statement in say a Saved Search what's the difference between Double quote vs single quote? (" vs ')

In a script (even if you are creating a saved search or it's associated formula), because you are necessarily writing javascript, It's okay to use any. But when you are writing a function in Saved Search UI, it's a good practice to use Single Quotes for string literals and Double Quotes for any Identifier. Because you are writing an Oracle SQL (or using the Oracle SQL functions and expressions), so makes sense to follow the Oracle standard.