Specifications are a more detailed than scope and often follows on from that process. When we talk about digital transformation, a level of specification is of course required, but there is a balance to be had in terms of the amount of time and effort that is put into detailing specifications for every minutia of the project.
Waterfall is the term used when there is an absolute specification for the entire solution and depending on the size of the project this can be a very time consuming and costly exercise.
Agile is a more modern approach, where the project progresses with iteration and continuous feedback and therefor consumes less time in constructing the detailed specification required within the waterfall method.
There are several other methodologies that may be considered; prototyping and spiral are examples, each have their own strengths and weaknesses, and therefor careful consideration should be applied at the outset as to the level of detail required at the initial specification stage.