Fontset uses the Google Fonts API, to subset a font based on characters you need, creating a tiny font to self-host.
Subsetting fonts is the process of taking a large font file as input and creating other smaller files, with fewer characters or OpenType features. — Creating Font Subsets
You don't have to install anything, or understand unicode ranges but the downside is that you're limited to Google Fonts.
I wrote a detailed post on using fonts on the web explaining everything in great detail.