Fred algorithm

Please explain me What is Fred Algorithm?

Google Fred is an algorithm update that targets black-hat tactics tied to aggressive monetization. This includes an overload on ads, low-value content, and little added user benefits.

This new algorithm update, simply known as “Fred”, is believed to primarily target websites with low-quality content and backlinks. Often, these two factors occur simultaneously and on websites that have utilized SEO companies to quickly build low-quality content and backlinks.

“Fred” is just a humorous euphemism that Googler Gary Illyes made up on the spot when pressed for a name for an unconfirmed, hypothetical update that a small percentage of (mostly) aggressive Web marketers attributed to March 7, 2017 or thereabouts.
Googlers John Mueller and Gary Illyes did confirm that something probably changed on that date because it was a Tuesday and Google rolls out changes to its live search engine “on average” (according to Illyes) about 3 times a (week)day.

Google Fred was a series of updates that occurred in March of 2017. While Google was vague about what this update specifically targeted, SEOs determined that Google Fred primarily affected low-quality, ad-heavy sites with thin content and bad backlinks.