Waterfall is a classical linear and sequential approach to software design and systems development. It includes Requirement Analyses, design, development, test, release and maintain, 5 main phases, each of them has its distinct goal. In software engineering, we named this as one of SDLC (Software Development Life Cycle). This methodology original from PDLC (Product Development Life Cycle). Now many companies still look at software products more than projects. So for most case, waterfall methodology will be used on more visible and more predictable software products.
Scrum is a lightweight Agile project management framework, mainly used for software development. It described in iterative and incremental approach for project work. So scrum framework shows development work more project-like.
Agile methodology is from project management, which build unpredictable task in nature way, because it’s using iterative and incremental work cadences, also called sprints, The development is accessed with these iterations of sprints, at the end of each sprint, an increment of work is presented by the team developing the project.
I saw there are many articles discussed Scrum vs Waterfall, actually, in waterfall, especially in development and testing phase, there are many loops like sprints; also in scrum, it also can have analysis, design, development, and testing cycle. So these two methods is not against each other, just find out a way to fit your software development work, not argues.