When we do a fit-gap analysis, we look at the company's processes and define what we can and cannot do with the standard package. When a business process can be handled with the standard software we call this a Fit. When this cannot be done it's called a Gap. All gaps have to be either developed or we need to purchase an add-on.
However, even when something could be done with standard software features it does not necessarily mean that doing this is wise. The standard application should be used for what it is designed for. Using standard features for something else might work in the current version but if it changes in a new version it might no longer fit. For this reason it is better to design something new instead of wrongly using standard features.