RTE is an extension of the TYPO3 system that is added to the TYPO3 package. RTE is a kind of WYSIWYG ("What You See Is What You Get") text editor. RTE provides similar functionality to rich text editors like OpenOffice Writer or Microsoft Office Word.
We can call extension rtehtmlarea as one of the important extensions in TYPO3. But this extension has some replacements, such as the following:
TYPO3 RTE provides functions such as formatting with bold, italic, underline, adding headers, paragraphs, line breaks, or adding images and tables to the text. You can choose different RTE configurations—Basic, Advanced, or Custom, which you can manage in the Ext Manager extension settings.