Look at these uses of ceci and cela in context:
L'environnement est une cause importante. Je comprends cela.
The environment is an important cause. I understand that.
Ceci est essentiel donc soyez attentifs à la leçon.
This is essential so pay attention to the lesson.
Cela dit, il est quand même un très bon ami.
That said, he's still a very good friend.
Ceci and cela (this and that) refer to an indefinite expression or an idea.
Like in English, 'ceci' (this) is used when introducing the notion, whereas 'cela' (that) is refering to an idea already mentioned.
Faire mes devoirs ou dormir, je préfère ceci plutôt que cela.
Doing my homework or sleeping, I prefer this rather than that.
Note: when they are both used, ceci usually refers to the 'former' and cela the 'latter' idea.
In a more common, less formal speech, you can also replace ceci and cela indiscriminately with ça .
ATTENTION: fixed expressions such as ''that said'' (cela dit) can never become ça dit.
Learn more about these related French grammar topics
Examples and resources
Cela dit, il est quand même un très bon ami.
That said, he's still a very good friend.
Faire mes devoirs ou dormir, je préfère ceci plutôt que cela.
Doing my homework or sleeping, I prefer this rather than that.
Ceci est essentiel donc soyez attentifs à la leçon.
This is essential so pay attention to the lesson.
L'environnement est une cause importante. Je comprends cela.
The environment is an important cause. I understand that.

Lukas
Kwiziq community member
26 October 2017
3 replies
Cela étant dit = That being said?
One of the test questions was to translate "That being said" to French. Is "Cela étant dit" a correct translation? It was not accepted as such, but some web searching shows that at least other people think that one is correct in addition the official answer "cela dit".
Chris
Kwiziq community member
26 October 2017
26/10/17
-- Chris (not a native speaker).
Ron
Kwiziq community member
26 October 2017
26/10/17
Je suis d'accord avec Chris. J'ai utilisé «cela dit» et je l'ai aussi entendu usé.
Lukas
Kwiziq community member
4 November 2017
4/11/17