Used in almost exactly the same way as ‘the former’ and ‘the latter’ in English,
前者（ぜんしゃ） and
後者（こうしゃ） and two nouns that appear frequently in Japanese. The 副助詞（ふくじょし） (adverbial particle) は will appear after these words, to express contrast between the two.
前者（ぜんしゃ） will be used for ‘the former’, while 後者（こうしゃ） will represent ‘the latter’. Both
前者（ぜんしゃ） and
後者（こうしゃ） appear at the beginning of their own statements, with a specific comment about each being made after は.
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どの大学（だいがく）に行（い）くか迷（まよ）っています。前者（ぜんしゃ）は家（いえ）に近（ちか）いが学費（がくひ）が高（たか）い、後者（こうしゃ）は家（いえ）から遠（とお）いが学費（がくひ）が半分（はんぶん）ぐらい安（やす）い。
I am undecided on which college to go to. The Former is close to my house, but the tuition is expensive. The latter is far from my house but the tuition is almost half the price.
地下鉄（ちかてつ）と新幹線（しんかんせん）、前者（ぜんしゃ）は地下（ちか）をゆっくりとはしり、後者（こうしゃ）は速（はや）いスピードで地上（ちじょう）を走（はし）る。
Subways and bullet trains. The former runs slowly underground, and the latter runs above ground at a high speed.
Statements made that use
前者（ぜんしゃ） and
後者（こうしゃ） require some sort of relationship in what is being compared. Usually, this will be obvious within the context of the sentence, but is something that you will need to be careful of when making your own sentences.
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こっちの車（くるま）とこっちの車（くるま）どっちを買（か）おう。前者（ぜんしゃ）は安（やす）くて古（ふる）くて、後者（こうしゃ）は高（たか）くて新（あたら）しい。 (Natural)
This car and this car, which should I buy? The former is cheap and old, and the latter is expensive and new.
明日（あした）動物園（どうぶつえん）に行（い）くか今夜（こんや）本（ほん）を読（よ）むかで、迷（まよ）っています。前者（ぜんしゃ）は動物（どうぶつ）がいて空（す）いている、後者（こうしゃ）は寝（ね）る前（まえ）にゆっくりできる。 (Unnatural)
I am undecided on whether to go to the zoo tomorrow, or to read a book tonight. The former has animals and isn't crowded, but the latter is relaxing before bed.