1. Yes, you NEED to know this!
The Ablative Case
Yes, you NEED to know this! 1

2. The Ablative Case
#1) The ablative of PLACE WHERE uses the Latin prepositions sub or in to indicate the place where a person or thing is located, e.g.,
Cornelia sub arbore sedet.
Cornelia is sitting under the tree.
Servi in areā stant.
The slaves are standing on the threshing floor.

3. The Ablative Case
#2) The ablative of PLACE FROM WHERE uses the Latin prepositions ab, ex or de to indicate the place where a person or thing is coming or going from, e.g.,
Puella a villā rusticā ambulat.
The girl is walking away from the country house.
Lupi e silvīs currunt.
The wolves are running out of the woods.

4. The Ablative Case
#3) The ablative of ACCOMPANIMENT uses the Latin preposition cum to indicate the person with whom something is done, e.g.,
Cornelia cum Flaviā ambulat .
Cornelia is walking with Flavia.

5. The Ablative Case
#4) The ablative of MANNER uses the Latin preposition cum to indicate the way in which an action is performed, e.g.,
Vilicus magnā cum irā clamat.
The overseer shouts with great anger.
N.B. Sometimes the cum is omitted. This phrase can also be translated like an adverb: The overseer shouts very angrily.

6. The Ablative Case
#5) The ablative of MEANS does not use a Latin prepositon, but indicates the object with which or by which an action is performed, e.g.,
Cornelii Romam raedā iter faciunt.
The Cornelii travel to Rome by means of a carriage.
The Cornelii travel to Rome in a carriage.
Davus Getam baculo verberat.
Davus strikes Geta with a stick. .

7. The Ablative Case
#6) The ablative of TIME WHEN does not use a Latin prepositon, but indicates the time when an action was, is, or will be performed, e.g.,
Secundā horā, Cornelii Romam descedunt.
At the second hour, the Cornelii depart for Rome.
Brevi tempore omnes servi sunt in areā.
In a short time, all the slaves are on the threshing floor. .