A brand guideline describes the logo itself: allowed versions, clear space, minimum sizes, and correct and incorrect uses. Anyone who puts your logo into a presentation or a banner reads it, which makes it the simplest way to keep it looking the same everywhere.
A visual identity guideline organises the system around the logo: colours, typography and rules for laying out materials. It makes sense once materials are produced in several places at once, some by you, some at the printer, some at an agency. When you are not sure which one is enough, we advise the brand guideline, since a full identity guideline can always be added later.
Branding is a level above and is not the same as a logo design: what the brand promises, who it speaks to and what sets it apart. A drawing does not settle that, brand strategy does. If that answer has not been given yet, we will say so before we start drawing.