But the page does show you the internals of what it does, it's just that it's done in a very high level, enough for the non-technical people who will most benefit from that page:
"The trick is to compute passwords rather than generate and store random passwords.
LessPass generates unique passwords for websites, email accounts, or anything else based on a master password and information you know."
"It does not save your passwords in a database.
It does not need to sync your devices together.
"
"The system uses a pure function, i.e. a function that given the same parameters will always give the same result. In our case, given a login, a master password, a site and options it will returns a unique password."
I'm a technical person, and I thought this was a great and fast explanation to tell me what was going on. I don't need any more details than this and appreciated the brevity.
"how it works" should show you the internals
"what it does" is better description if you are just going to tell me the inputs and outputs.