A marketing communications company (or marcom) will work with you to grow your business and achieve your business goals.
Marcom's can provide you with services that cover all stages of your business marketing cycle. These services include market research, logo design and branding, development and implementation of strategic marketing plans, design and production services for creating your advertising collateral, and evaluation of all elements of your existing marketing strategies.
Their involvement in your business can range from one-off involvement in a particular strategy (such as developing a website or brochure) to managing your overall business marketing (such as developing a perpetual email marketing program in concert with the development of a new website and more).
A marcom specializes in marketing, and therefore has the time and expertise to focus on developing and implementing strategies specific to your business, and that will achieve you results.
A marcom can help you think outside the box. They often work across a range of different industries and so can bring diverse perspectives and experience to the table.
Most importantly of all, utilizing a marcom as a part of your business plan shows a maturity in business development. Those who need medical attention, turn to a doctor and those who are looking to grow their business, turn to a marcom. By seeking external advice and expertise, you can ensure your marketing decisions are not made in isolation and that your strategies are effective and realistic.
Wikipedia Definition of Marketing Communications (Marcom)
Marketing communications is focused on product/produce/service as opposed to corporate communications where the focus of communications work is the company/enterprise itself. Marketing communications is primarily concerned with demand generation, product/produce/service positioning while corporate communications deal with issue management, mergers and acquisitions, litigation etc.