As Wikipedia puts it:
PowerShell or Microsoft PowerShell (formerly Windows PowerShell) is a task automation and configuration management program from Microsoft, consisting of a command-line shell and the associated scripting language.
I think of it as a much more capable version of the Command Prompt in Windows. And it works for all sorts of more complicated tasks... you can certainly delete a folder full of files, or just certain files using explorer, but as in an example I ran into earlier this week, where I needed to delete one recurring folder inside 100+ folders, sometimes using Explorer can be time consuming and tedious. With Powershell, deleting those folders, and all the files in them, took entering one command & pressing Enter. Done. The following linked article shows how to do that sort of thing, and more, like getting rid of certain files based on their age. While some of the stuff you can do using Powershell can seem super complicated, it's extremely popular, and there are millions [maybe billions] of examples and scripts online to do more than you likely ever thought possible, so if/when there's something you're unsure how to accomplish, Google.
adamtheautomator[.]com/powershell-delete-file/