Don't Understand A Phrase Appeared After Creating A New Category

Multi-Vendor Questions
1
Dear all,
after creating a new category this phrase appeared:
"NoticeSome HTML tags that you have used were cut off because of the restrictions on inserting HTML tags such as ,
what is the meaning of this phrase
Regards.
Magdy Galal
2

The system removes some tags from descriptions due to security reasons.

3

thanks