Some people are confused on the difference between project management and the project lifecycle. It takes both types of work to complete a project successfully. The general difference is that project management is used to define, plan, control, monitor and close the project. The work associated with actually building the project deliverables is accomplished through work that is referred to as the "lifecycle." Project management is used to build the schedule, but the vast majority of the work in the schedule is the lifecycle work associated with building the project deliverables.
Projects can be managed using a common set of project management processes. In fact, one of the valuable things about having a common project management methodology in your organization is that the same processes can be used on all projects.
What makes a project unique are the deliverables that each project builds. For example, building a bridge is a different type of project than building an IT solution, or building a new consumer product. The lifecycle describes the activities used to build the deliverables and is generally unique for each project.
Even though all projects are unique, there are still common lifecycle models that can be used to build deliverables in similar ways. The generic "waterfall" is an example of a lifecycle model. In a waterfall project, you start off understanding the requirement of the solution, designing a solution, building and testing a solution and then implementing the solution. Each of these major areas of focus is called a phase (Analysis Phase, Design Phase, Construct Phase, etc.) What could be easier? The classic waterfall approach is the lifecycle model you would probably end up with if you knew nothing about methodology and just had to build a project workplan from scratch.
Although the waterfall model can be applied to all projects, other lifecycle models might be more efficient and effective based on the characteristics of the project. For instance, if you're installing a software package, you can utilize a specific lifecycle model for package implementation that is light on the design and construct phases. Likewise, if you're conducting a research and development project, you can use a specific R&D lifecycle model that takes into account that the work might be thrown away when you're done. If you're building a marketing campaign, there's a general lifecycle model that can describe the activities to be successful. Building a house is certainly complex, but a basic home-building lifecycle model will probably cover 90% of the work on almost all home construction.
I've been in many organizations that say they have a good project management process, but the process actually describes the lifecycle, or execution, portion of the project. If your project does not include both the lifecycle and the project management activities, you'll be less likely to be successful than if your schedule includes both important components.