Phishing is a fraudulent technique that is used to steal personal data (for example, a username and password for an email account, phone numbers, or bank card data). Sites that use phishing “pretend” to be other sites that are popular and well-known. They usually look pretty much alike and even have a similar domain name. This way they are misleading site users and may make them pass their personal data to the site owner, not knowing that they are being deceived.
Phishing pages often appear as a result of hacking a decent site that isn't fraudulent. Moreover, the site administrator might not even know about it. If your site is suspected of phishing, it might have been attacked and implemented phishing code. Carefully check the site following the recommendations in the How to clean an infected site and How to protect your site from infection sections.
After removing malicious code, you can speed up the removal of the website's threat warning by sending it to be rechecked. To do this, use the I fixed it button on the Security and violations page in Yandex.Webmaster. In most cases, it takes a few days.