I can assure you that there’s no difference as per the usage of “c’est/ce/cet/cette”. As a native french speaker, I’ve always struggled to understand the difference between this and that, and I’m still often making mistakes when I speak english since I’d use “ce” for everything in French.

However:

• If you want to stress a “this”, you should use “celui-ci” (“celle-ci” f.), which means “this one”
• If you want to stress a “that”, you should use “celui-là” (“celle-là” f.), which means “that one”

But these expressions would rather be used when there is a confusion between designated subjects, as an answer to “which one ?”.

If you want to say “this right here is,” you can say “Ceci est…”.

Likewise, if you want to emphasize “that thing over there,” you can say, “Cela est…”

Both of these constructions are more characteristic of written French (and formal spoken French, like a newscast or a pre-written speech) than the everyday language.

Je suis d’accord avec Jean.

I replace could with should as….

If you want to stress a “this”, you should use “celui-ci” (“celle-ci” f.), which means “this one”

If you want to stress a “that”, you should use “celui-là” (“celle-là” f.), which means “that one”

Many wrong or partially wrong answers here, and your question is not precise enough. The use of demonstrative pronouns is not easy. Here are my thoughts after I’ve read the answers, probably not exhaustive.

Note the use of ci and là in French:

• Ici = here
• Là = there
• Celui-ci/celle-ci = this one
• Celui-là/celle-là = that one
• Ceux-ci/celles-ci = these ones
• Ceux-là/celles-là = those ones

Now let’s begin.

• This + noun for ce/cet/cette + noun

I want this balloon!

Je veux ce ballon !

If you want to insist more:

Je veux ce ballon-ci !

It means not another one, this one.

• That for ce/cet/cette

No, I want that one! That ballon!

Non, je veux celui-là ! Ce ballon-là !

• This in this is

If you say:

It’s a beautiful dress!

You translate it into:

C’est une belle robe !

But if you say:

This is a beautiful dress!

You probably want to insist on this dress, so you could say:

Cette robe est belle !

Cette robe-ci est belle !

• That in that is

That is a beautiful dress!

Could be translated into:

Cette robe-là est belle !

But we would rather say:

Ça, c’est une belle robe !

In many cases, you can’t use -là to translate that:

That is something!

Ça, c’est quelque chose !

That is strange.

Ça, c’est bizarre.

• Example

This building is empty. It’s strange. Yeah, this is really strange. But the strangest thing is that it is closed. That is very strange.

Cet immeuble est vide. C’est bizarre. Ouais, c’est vraiment bizarre. Mais la chose la plus bizarre c’est qu’il est fermé. Ça, c’est vraiment bizarre.

La différence entre ceci et cela est une notion de proximité

On emploie de préférence ceci pour désigner quelque chose de proche, et par opposition, cela pour désigner quelque chose de plus éloigné.

C’est vrai pour un éloignement géographique mais aussi préférentiel : si mon choix se porte plutôt sur un bonbon à la fraise plutôt qu’un autre bonbon à la framboise, j’utiliserais celui-ci pour désigner le bonbon à la fraise, et celui-là pour le bonbon à la framboise.

Pour s’en souvenir facilement, il suffit de revenir à l’origine de ces expressions :

• Ceci => Celui-ci (ou *celle-ci) renvoie au mot ici.
• Cela => Celui-là (ou *celle-là) renvoie à l’expression là-bas.