Container element (HTML)
In HTML, a container element is an element with starting and ending tags. That is, it contains content, hence the name.
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For example, the <body> element is a container element since it contains all the body content within its starting (<body>) and ending (</body>) tags. The same applies to the <h1> element. And so for the <p> element.
The opposite of a container element is a non-container element, more commonly referred to as a void element.