The ablative case, as you saw in the previous chapter, can be used in place constructions (place where, place from which). The ablative also has a number of other uses. Here are two more:
Ablative of Accompaniment
The ablative is used with the preposition cum ("with") to show accompaniment. Accompaniment means that someone performs and action in the company of someone else.
Cornēlia cum Flaviā ambulābat.
Cornelia was walking with Flavia.
Sextus per urbem cum cane currit.
Sextus runs through the city with his dog.
Ablative Means or Instrument
The ablative is used without a preposition to show what object is being used to accomplish the action. In English, it is translated "with."
Senex baculō ambulat.
The old man walks with a stick.
Cornēlia Sextum librō pulsit.
Cornelia hits Sextus with a book.