This presentation, the first part of an extensive practical tutorial on logical and bit-stream preservation using Plato (a preservation planning tool) and EPrints (software for creating digital repositories), provides a rapid recap on the principles and reasons for digital preservation. The presentation was given as part of module 4 of a 5-module course on digital preservation tools for repository managers, presented by the JISC KeepIt project. For more on this and other presentations in this course look for the tag ’KeepIt course’ in the project blog http://blogs.ecs.soton.ac.uk/keepit/