C'est vs ilest

Question

Why is it c'est pierre and not il est pierre?

Cécile Janty-Davies · Accepted Answer

Hi Carol, 
Take a look at my answer to Jorge with a list of frequent errors with 'c'est/il est'.
https://french.kwiziq.com/questions/view/c-est-ma-mere-vs-elle-est-ma-mere
Also, look out for a fill-in-the-blanks I worked on this very matter which might help you with this conundrum.
Bonne Continuation!

Maarten Kamp · Answer

Carol, I note you found the answer in the discussion. Agree with you that a line noting this specific situation should be in the lesson - it is not fully covered as such presently, which explains the question appearing regularly. 
This link may give you further understanding:
https://www.lawlessfrench.com/grammar/cest-vs-il-est/