How to understand this sentence? And what's the meaning of "from" here?

Usually, it means he works at home three days a week. This is the most likely meaning.

It could also mean he goes directly from home to wherever his job takes him other than his normal place of work.

Why does it mean "it means he works at home three days a week. "? Why not use "he works at home"directly. I thought "from somewhere" meaned "leave somewehere,off somewhere".

"From home" is a relatively new expression.

'I work from home" means 'I work from my home office."

"out of my home" can also be used, along with "at home".

He might have calls to make as part of his job, or visits to make.
He can do these from home, instead of calling at the office first. There are several reasons why this might be a convenient way of working.
Otherwise, it can just be taken as meaning the same as "at home".