The waterfall process is a linear process of creating, done by only moving on to the next phase of a project once the prior phase is complete. There are pluses to the waterfall process, but if you go downstream too far it is often hard to get back on track.
This waterfall process used to be the core development processes of website creation, leading to one phase of planning. I have found though, that many businesses use this way of project management when working through any type project. The waterfall process can build a ton of momentum and undivided attention towards a project, which is usually a great thing. Though, when there is so much momentum behind a project from the early stages it can be really difficult to asses the projection of the project and allow for mid-project maneuvering.
Laying out the foundation in which you prefer to tackle a project before you even start the ideation stage, can change the outcome of the project drastically.