OP, this is absolutely not the case. If you install in a dual-boot configuration (recommended for beginners), not only will you not lose your data, you won't lose the ability to boot into Windows. You'll get asked to choose which OS you want each time you restart and Linux can access all files on Windows (but not vice versa). Secondly, not only is windows not the only OS that markets itself to Just Work™ (that's been MacOS's entire shtick since its inception), modern Linux does that as well. You can install software and drivers, manage system configuration, etc. without even knowing what a terminal is. Knowing how to use the terminal is never a bad idea, but rest assured that by no means do you have to, especially when starting out.

I sincerely doubt the person I'm replying to has used a distro marketed towards Linux newbies at any point in the last five years.