Difference between Rasa core and Rasa nlu

Question

I tried to understand about rasa from official documentation of Rasa core and Rasa nlu but not able to deduce much. What I am able to understand is

Rasa core is

Answer 1

A very layman description for starters: Rasa NLU: Its the interpreter which understands the input. Basically figures out entities and labels the intent.

Rasa Core: Does the rest of the work you want your bot to do. The flow of conversation being the most important thing.

eg: You say "Hello" to the bot. Rasa NLU will understand the input's intent as a 'greeting' and Rasa Core will tell the bot to reply with a greeting.

PS*: The reply back would be a greeting if you train your bot for it or it might be anything else as well.