If you are a small business, just starting out, your logo will probably want to show what you do, since a logo is an abbreviation of the words you would use to describe your business, like a shortcut. Once a prospect sees your logo the first time & they understand what you do, what you stand for, etc, the next time they see your logo it’s like a trigger to their memory that reminds them of what you are all about.
Above all it should be a visual representation of your company and your brand, a way to show what you do and what you can offer to customers in one simple graphic.