Web, domains and email
TXT
Abbreviation for text
In short and in plain language
A TXT record is an entry with text for a domain.
It sits in the address book of the internet. Services read it there.
They use it to check who owns the domain. Or they find rules for sending mail.
It does not change your website. The site looks the same as before.
Definition
A TXT record is an entry in a domain's DNS that holds free-form text. Services read it, for example, to check who controls a domain or to look up rules for sending email. It does not change how the website is displayed.