Need and Require are synonyms, and can almost always be used interchangeably. With that being said: Need has require in it's definition.
Need: Something required or wanted; a requisite.
Require: To have as a requisite
Requisite: Required; essential.
Essential: Basic or indispensable; necessary.
You can think of Entail like "involve" (they are synonyms)
Entail: To have, impose, or require as a necessary accompaniment.
A: I want to start a business!
B: What does that entail?
A: A building and a company name is essential. I'll require some employees, and they will need desks.
B: Good luck!
Hope that helps.