background.

Real background blur comes from the lens and cannot be added later. What software does instead is a convincing imitation, and knowing the difference tells you when it will look wrong.

Grey, white, blue, black or the room you are standing in. The choice is mostly about how much separation you need and how formal the destination is.

Cutting yourself out is the easy half. Making the result look photographed rather than pasted is the half that gets skipped, and it comes down to two small additions.

A true white background is a specific requirement, not a default. Here is who actually asks for one, why shooting it is harder than it looks, and how to fake it well.