Advertising is not just about saying something, it is about HOW you say something. The way it is written is a key factor in relating a layout to its intended audience. The audience has to feel they are being spoken to by a member of their group if the advertisement is to stick with them and be memorable. The type fonts chosen for the project have to be fonts that belong in the viewer's world or they will just be dismissed. The size, placement and density of words in a layout create a visual hierarchy that leads the eye around the layout with little effort from the viewer.
Information and how it is presented is just one part of the big design puzzle. So much goes into the visual elements of layout as well. A great deal of what happens in a well made logo, happens in the first few seconds of viewing it. The gestalt of a piece is the way a brain organizes the elements of the composition visually. This normally occurs subconsciously when you first look at a logo, sign or any well built design. It only takes a few seconds but it can be the most important factor in making a layout stick in a viewer's mind. It is also what makes a viewer recognize a logo when they see it again (very important for company branding). The first few seconds of looking at a sign is sometimes all the time a Designer has to attract a viewer or get the message across.
Relating to a target audience and keeping your company identity in their minds is tricky work. This is where the "Graphic" comes from in "Graphic Designer". A truly "Graphic" Designer will consider these and many more factors. Aside from the size, placement and hierarchy of elements in a layout, there are countless rules and factors to keep in mind. The timing and rhythm of elements in a created composition are as important as they are in a great song. And just like a song that has been composed properly, a properly created visual communication will stay in the mind of the audience. A good Designer knows all the rules of art. And when you know all the rules of something, you can then and ONLY THEN, know when to bend and break those rules in a way that is productive to the project. Good Designers can do this in a way that feels effortless and natural. Bad Designers don't even consider these important aspects.