In the early days of computing, physical hardware was confined to singular tasks, for example, calculators. As computers advanced, we began to be able to multitask, enhancing the ability to run simultaneous applications in parallel, such as running Microsoft Word while also having a web browser open and Spotify playing music in the background.
Virtualization is simply the evolution of a computer’s ability to multitask, whereby portions of resources from a single computer are divided among multiple smaller “virtual” computers. An analogy would be having a single pie and six hungry people (in this example, the hungry people are the applications in need of resources). You solve your problem by slicing the single pie into six pieces and handing them out to their respective hungry consumers (applications, etc.).