What’s in a Font? (.. no not something in a Spanish fountain – a Typeface !)

Microsoft has just changed its default font from “Calibri” to “Aptos” – what does that mean for me? This Thursday, March 7th, we will plough through the confusing mess of print and web fonts. When I copy and paste text from one app to another, why do the fonts and spacings all get mixed up? Why do some web pages look different on my phone and my laptop? I like fancy fonts, how can I be sure that a document I send by e-mail will look and print out OK when it’s received?