Once the responder receives the email it does a keyword search in a key-map directory full of word.map files in them are the potential mapping keywords to this words chunk and the code chooses the best match and looks up the chunk of text and concatenates it with the user input 
this changes the bots personality the more chunks the more it changes and adapts
It is the tool novice website administrator
needs to easily add a bot to their site for FREE
OneClick install walks you tbru entire install
Bring your own Domain Name and keys to sendgrid and OpenAI but use Ubuntu from digital ocean this will run in their 4 dollar a month 512 MB server better on a 2GB box 1 cpu it is 12 bucks, free credit at OpenAI 100 emails a day free at send grid
All in all total money spent to build your own bot with a domain name is under 10 bucks if you search well at go daddy
Good luck 
email me if you need any help