Expressing your mission in a simple way
Branding is the simplified expression of the vision of your company, and of its mission, it is very important because it allows understanding in a wink, by a sentence and the graphics, of the intentions of the founders and how they communicate those - clearly. If you cannot express your vision in a simple way, in a simple sentence by going beyond the definition of your product, you will have trouble convincing anyone that you are on the right track.
The tagline, logo, and graphics don't tell the whole story of your company on their own, but they are the subconscious of the story being told, of the emotional connection the customer goes through to trust you. Build your company this way to be credible.