How does the Builder pattern differ from the Factory pattern, given that both are considered creational patterns?

They solve genuinely different problems despite both being about object creation. Factory is about hiding which concrete class gets instantiated behind one method, so callers do not need to know or name the specific class themselves. Builder is about making the construction of one specific, often complex object readable and safe when it has many parameters, especially optional ones, regardless of whether more than one concrete class is involved at all. The two are not mutually exclusive — a factory method can internally use a builder to actually assemble the object it eventually returns, combining which class to create with how to safely construct it in a single call.