I would like to know how many fonts I have available.
Any reason in particular or just curiosity?
On the browser version, you will have web fonts + imported fonts available and on desktop version all of those + the system fonts (you have to check on your font management).
By now, webfonts are about 881 font families and with weight variations count up to 2000 fonts.
Here’s a font list: webFontList.pdf.zip (39.3 KB)
Here you can generate a static list http://yepcheck.com/gfontviewer/
or an interactive one https://ultra.zone/web_fonts