The four demonstratives
THIS is used to refer to someone or something close or near ("This Sunday we'll go to the beach.")
THAT is used to refer to someone or something not close or near ("That man on the other side of the street.")
THESE is the plural of "this" ("These pens don't work.")
THOSE is the plural of "that" ("Are those mountains in France or in Italy?")
In other words, this is near the speaker and is singular: ce...ci, that is not near the speaker and is singular: ce...là, these are near the speaker and are plural: ces...ci, and those are not near the speaker and are plural: ces...là.
The four demonstratives can be used with a noun ("substantive, nom") or without a noun. For example...
- This restaurant is quite expensive. Let's try another one. (vous êtes devant le restaurant).
- That's an expensive restaurant. Let's try another one. (on vient de nous dire "Let's have lunch at Fouquet's")
Think of it this way: Si une action est proche dans le temps, nous utilisons this: ceci ou those: ceux-ci.
Par contre si une action est terminée ou se situe dans le passé, nous utilisons that: cela ou those: ceux-là.