One function of marketing communications is to help differentiate an offering (brand, product, service, idea) from competitors in the marketplace. This is especially important where the offering competes in a largely undifferentiated marketplace (as in fast moving consumer goods (FMCG) categories). For example, many supermarket goods are essentially the same product (varieties of tinned tomatoes, dried pasta, cooked meats) and so it is often the communications surrounding these offerings that allow them to stand out.
In many cases, marketing communications can be extremely successful in this regard. For example, it is not uncommon to refer to whole product categories through the name of the brand leader, so synonymous have many of these relationships become:

- In the UK we might refer to the Hoover instead of the vacuum cleaner.
- In the US you might Xerox something rather than photocopy it.
- Jacuzzi is not a product but a brand of Italian hot tub.
- Bic, a common term for a disposable pen, is in fact the brand name of a French manufacturer of this product
- We use the term Thermos when referring to an insulated flask, but Thermos is the name of a German brand
- And we are more likely to 'Google it' than search the web

Marketing communications can also be used to help reinforce experiences of product use in one of two ways:

- It might take the form of after-sales service or purchase protection cover and/or involve various forms of follow-up incentive to encourage repeat purchase through coupons, discounts or loyalty programmes.
- Alternatively, marketing communications might be employed to remind people about the availability and value of a particular offering. This can take many forms such as reminder advertising campaigns for well-established brands, or a direct mail shot into your email inbox.

A key role for marketing communications is to inform the audience and/or potential customers about an offering. This might take the form of advertising a new product or providing additional materials through catalogues, brochures, a press release, or personal selling.
This is an especially important function in the context of new product launches when there is a need to create awareness. It is also important for high involvement purchases and those that are highly complex, such as financial services, new cars and medical services.

Historically, the main role of marketing communications has been to persuade potential customers of the desirability and value of the offering and to entice a purchase. Marketers use incentives, seductive advertising, tempting offers, and skilled salespeople to help move the customer from interest to purchase.