A logo mark represents the brand, something that becomes recognisable and associated with that particular brand. There are different versions:
Pictorial - a logo mark which represents something such as Twitter = Bird
Abstract - deeper meaning, shapes, doesn’t represent anything = Pepsi
Combination - Logo mark and word mark together = Ralph Lauren
Emblem - logo within a shape = Ikea
Dynamic - Will change depending on the application - adaptable - versatile
A design program is all of these different areas combined!
It also includes colour, selected typefaces and an extra decorative element = a pattern
The use of this helps customers recognize it from anywhere like Apple or Pepsi, because they are so simple the become easily understandable for the user.