This isn't an opamp (operational amplifier). It isn't even a differential amplifier.  

- > Why would they say it's DC when it's effectively not.  

  Because the input of the amplifier is DC coupled to the output.  

  [![enter image description here][1]][1]  

  It *could* theoretically be used for amplifying a signal with a DC component, although in most applications this isn't required. The schematic you posted is just a hint, showing a *typical application* of the chip, it's not the *only* way to use it.  

  [1]: https://i.sstatic.net/nYDDs.png