Celle-ci est en coton, mais celle-là est en laine.

They mean this one and that one.

• celle-ci = this one
• celle-là = that one

They are used when the noun is not repeated, but it is understood from the context.

Because celle is the feminine singular form.

French demonstrative pronouns change depending on the gender and number of the noun they replace:

• celui = masculine singular
• celle = feminine singular
• ceux = masculine plural
• celles = feminine plural

So this sentence must be referring to feminine singular items, such as a shirt, a jacket, a scarf, or any other feminine noun.

They help distinguish between this and that.

• -ci means something like here / this one
• -là means something like there / that one

So:

• celle-ci = this one
• celle-là = that one

These endings are often used when you are contrasting two things, exactly like in this sentence.

Yes. That is exactly what they do.

They replace a noun that has already been mentioned or is obvious from the situation. For example, if you are looking at two sweaters, you can say:

• Celle-ci est en coton
• Celle-là est en laine

You do not need to repeat the noun if both people know what you are talking about.

French often uses être en + material to mean to be made of a material.

So:

• être en coton = to be made of cotton
• être en laine = to be made of wool

This is a very common pattern for clothes and objects.

Examples:

• La chemise est en coton.
• Le pull est en laine.

For materials, French commonly uses en after être.

So you usually say:

• en coton
• en laine
• en soie
• en cuir

Using de here would usually not be the normal choice in this kind of sentence.

A good basic rule is:

• être en + material = to be made of + material

Because after en in this structure, French usually does not use an article.

So you say:

• en coton
• en laine
• en bois
• en métal

Not normally:

• en le coton
• en la laine

This is just the standard pattern with materials.

Yes, especially if you are comparing two items directly.

Celle-ci ... mais celle-là ... is very natural when pointing out a contrast between two things.

That said, in casual speech, French speakers do not always use -ci and -là so carefully. Depending on the situation, people may also rely on pointing, stress, or context. But this sentence is completely correct and natural.

It is a demonstrative pronoun.

That means it points to something specific, like this one or that one, while replacing a noun.

So instead of repeating the noun, French uses a pronoun:

• noun repeated: Cette veste est en coton, mais cette veste-là est en laine.
• noun replaced: Celle-ci est en coton, mais celle-là est en laine.

The second version sounds much more natural if the noun is already clear.

Because each part has its own subject.

The sentence has two clauses:

• Celle-ci est en coton
• mais celle-là est en laine

Each clause needs its own verb, so est appears twice.

English works the same way:

• This one is cotton, but that one is wool.

You know from the context.

Because celle is feminine singular, it must replace a feminine singular noun. The exact noun is usually obvious from what was said earlier or from what the speakers are looking at.

For example, it could refer to:

• la chemise
• la robe
• la veste
• la jupe

If the missing noun were masculine singular, you would need celui-ci instead.

The demonstrative pronoun would change to match the noun.

Forms:

• celui-ci / celui-là = masculine singular
• celle-ci / celle-là = feminine singular
• ceux-ci / ceux-là = masculine plural
• celles-ci / celles-là = feminine plural

Examples:

• Celui-ci est en coton, mais celui-là est en laine.
• Celles-ci sont en coton, mais celles-là sont en laine.

Also notice that the verb changes in the plural:

• est for singular
• sont for plural

A simple pronunciation guide is:

sel-see ehz ahn koh-tohn, meh sel-lah ehz ahn len

A few useful notes:

• celle sounds roughly like sel
• ci sounds like see
• là sounds like lah
• mais sounds like meh
• laine sounds like len

In natural speech, it flows together smoothly, and the final consonants are often not strongly pronounced unless they are meant to be.

No. That would not be correct here.

Cette is a demonstrative adjective, so it must come before a noun:

• cette robe
• cette veste

But celle-ci and celle-là are demonstrative pronouns, so they stand on their own and replace the noun.

So:

• correct: cette robe
• correct: celle-ci
• not correct: cette-ci

Not in natural English.

French uses en here, but the natural English translation is made of or simply is cotton / is wool, depending on context.

So the best idea is:

• est en coton = is made of cotton
• est en laine = is made of wool

It is better not to translate en word for word as in here.