What is a Root CA and Intermediate Certificate? (86/285 technotes for 2015)

• The Root certificate has the private key issued by the CA (Certificate Authority). 
• This is set offline and has to be in a secured location as it contains the private key.
• From the Root CA - 2nd Level / Intermediate Certificate’s are generated
  
• 2nd Level Certificates are responsible for issuing certificated to any websites which require certificates.

• In order for the browser accesing a website to trust a certificate, the browser has to be pre-loaded with the Root Certificate (the red arrow).

References:

https://youtu.be/LRMBZhdFjDI