Please when you create a and sell to a company how will they managed it without knowing how you code it

Answer 1

You're missing an important word in your question and maybe we need some more information. However, you've included "website" in the tags, so I imagine that's what the question is mostly about.

Depending on what type of website you're creating, there may be different possibilities. A large part of creating any product comes down to UI/UX.
The interface, how something looks and perhaps what signals you can provide to influence or guide a user, plays a big role. People can use a search engine or a Web based email without having to know how it is coded. They also don't need much in the way of formal instructions. This is the case when the interface is intuitive, easy to understand and it gives the correct or expected response to any user's action.
That then makes the user happy.