1. "C'est" - This is used when referring to something or someone. It is a contraction of "ce" (this) and "est" (is).
* Example: "This is a book." - "C'est un livre."
2. "Ceci est" - This is used when referring to something that is near or close to the speaker.
* Example: "This is my pencil." - "Ceci est mon crayon."
So, depending on what you're talking about, you can use either "C'est" or "Ceci est" to say "This is" in French.