Yes. The first installed font is used, so in your case, the Georgia font is used if it is installed. If not, use Times New Roman. If none of them are installed, the Sans-Serif font will be used. (Yes, Sans-Serif is not the name of a particular font, but the name of a family of similar fonts, without the so-called serifs .)
When it comes to the "em" unit, see W3C Schools .
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