Many confuse all three subjects and frankly I can see why. Each one crosses over with the other but in essence they have three very different meanings. In an attempt to simplify and explain the differences I thought it would be easier to compare the three to something everyone can relate to…….A Human Being.

If your business were a person then the brand is the heart and brain. As a person we all have a past, present and future, values, morals and character. This is your business brand, who you are and what you stand for.
Like the heart and brain, a brand may not be something that you can physically see at face value but its constant representation into real life events signify the difference between you and the next business, creating a piece by piece visual synopsis of your business brand.

If your business were a person then the Corporate Identity would be the body and clothes. A persons visual identity is made up of hair, clothes, face, skin tone etc. making that person unique to themselves. Each person looks/dresses differently according to the way their head and brain tell them to. Likewise your business identity is made up in a similar structure. Your logo, stationery, websites, vehicles, signage, clothing etc are all assets reflected by your brand and visible for all to see.
A corporate identity is the brand in a visual form, something recognizable yet different.

If your business were a person then design would be your taste and image, an incorporation of how your identity is perceived. As a person, design is incorporated into how your hair is cut, what clothes you are wearing and what colour they are. Whether you are a fashion freak or not, each aspect reflects you as a person and communicates a message.
In business, design focuses on the same aspect and specialises in fine tuning the message of your brand through your identity. Any business can have a company logo but how that logo is created and used with your business is essential as a first and last impression to the public. Just as humans choose to look a certain way, design dresses up a business with a strategic method.

The heart & brain is the business brand
The body and clothes are the corporate identity (Visualisation of the brand)
Fine tuning the body, clothes, brain and heart would be the graphic design.