Pre-biased Bipolar Transistor (BJT) Tradeoffs

Pre-biased (also "resistor-equipped" or "digital") transistors indeed have a plain resistor in front of the base. Most also have a second resistor between base and emitter. Both resistors are used in exactly the same way and for the same purposes as external, discrete resistors.

Creating resistors on a silion die is harder, so they have looser tolerances, often ± 30 %. (For digital switching, where all you care about is that the transistor is saturated, this does not matter.) Otherwise, there is no difference.

As CL. said they have one or two built-in resistors.

In addition to saving board space and money they also idiot proof if you use them within reason.

Often the base resistor is dimensioned that even if you turn the transistor on the collector won't conduct more current than the part can handle. With typical digital circuits that stay below 5V these parts will also not disipate more power that they can handle, even if you accidentely switch Vcc directly to ground without any load.