When an business is small you do not need to think about IT organization, each has his PC with office software, webbrowser, e-mail and some business-specific programs. But IT continues to grow, there will be an extra printer then a a server, a webpage is installed with a provider, etc., etc.
By then it is time to think about making a plan what one wants to achieve with his IT. Which primary operating processes are to be supported, how much of my revenue is it allowed to take? IT planning requires a comprehensive approach, where hardware, software, security and usage policies are defined and where possible scenarios are described for disasters. It's not just about devices or programs, but to the way people deal with IT.
The biggest disasters in the IT sector are caused by employees who, intentionally or not, catch viruses that can delete files on your system, leave computers unobserved so that everyone has access to your business data.
The current tendency is to bring more and more functionality on the web, you share documents, calendars, emails and project plans on the web, even entire departments with designers share technical drawings. By then it is more than necessary to talk about security because no organization will wants to show the public and all of its competitors it's businessplans. On the other hand, it may be useful to present a specific task very well in public.
Sometimes seeing the own organization through the eyes of an outsider can be very helpful. With an analysis of business processes you can always find things that you can improve, if you want to implement IT-systems properly, you have to make such analysis. You as a businessman/woman will decide how and which changes should be made, because you know the backgrounds.
In short, the more you use IT the more you need to organize it and thus reflect on the whole organization. The aim of computer use must always be to save costs, increase revenues, or increase services, it should never be a goal in itself.