In your Dashboard > Appearance > Themes you may see Legenda parent theme and child theme.
A WordPress child theme is a theme that inherits the functionality of the parent theme. With child theme you can make modification or add additional functionality to parent theme. A child theme is the safest and easiest way to modify an existing theme, whether you want to make a few tiny changes or extensive changes. Please read more https://codex.wordpress.org/Child_Themes
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