In a desktop word processing program such as LibreOffice Writer or Microsoft Word, the program relies on the fonts that are installed on your local computer. With Google Docs, that isn’t the case; for one thing, the program cannot guarantee that you’ll have the required fonts installed.
Google Docs uses Google’s own web-based fonts. A few of the more popular fonts are available in the program by default, and can be seen when you click the Font drop-down menu on the toolbar. Many others are available, though, and to access them just click the More Fonts … option at the bottom of the Font menu.
These fonts are displayed, by default, in decreasing order of popularity. However, you can use the Sort menu to choose a different order.
To make a particular a font to Docs, just click the font name. This will send it to the My Fonts column on the right hand side of the dialog box.
When you dismiss the More Fonts dialog, the font is immediately available to you in the Fonts list.