Custodians of digital content take action when the material that they are responsible for is threatened by, for example, obsolescence or deterioration. At first glance, ideal preservation actions retain every aspect of the original objects with the highest level of fidelity. Achieving this goal can, however, be costly, infeasible, and sometimes even undesirable. As a result, custodians must focus their attention on preserving the most significant characteristics of the content, even at the cost of sacrificing less important ones. The concept of significant characteristics has become prominent within the digital preservation community to capture this key goal. As is often the case in an emerging field, however, the term has become over-loaded and remains ill-defined. In this paper, we unpack the meaning that lies behind the phrase, analyze the domain, and introduce clear terminology.