Elementary icon set is default in Elementary OS, it is provided by Danrabbit.
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Owner and main writer of MintGuide.org is not a native English speaker.
Elementary icons offers over 7,500+ icons for Linux desktop. This icon set is well polished and looks really nice with all kind of light and dark themes. There are two versions of Elementary one is "Elementary" it can be used with light themes.
sudo add-apt-repository ppa:noobslab/icons sudo apt-get update sudo apt-get install elementary-icons