It is simply an algorithmic appraisal based on recent sales, your purchase price, etc. 

But as @Jacob Atkinson points out, it's hard to remember all of the upgrades and the algorithmic solutions out there do the same things. 

The bookies are not trying to pick winners, they're trying to split the market.On top of that, unlike appraisers, they need to assess thousands of parcels annually and therefore generate algorithms to do this as efficiently as possible.So assessed values may be wildly inaccurate for the following reasons:Poor algorithms / methodsStatute (or lack of resources) requiring infrequent reassessments in a changing marketAnomalous properties that have features that can't be adjusted in a wholesale fashionThe assessed value can be a great tool if you understand how your county is arriving at that value. 

FICO's algorithms are a trade secret, but folks have done their best to reverse engineer. 

The scammers have an Algorithm on the title company e-mail  that looks for certain words that trigger an email sent out right at the same time the title company does.So, my buddy sent 195k to account in a Wells Fargo account on closing.

@Kimberly KlaasIf you do searching on google there are ways you can manipulate the algorithm to place your website at the top of the search when people use certain keywords.

@Richie Choy given the responses, it may be helpful to link out to a few past projects or overviews around machine learning.While automation tends to be something many understand, most still do not appear to grasp ML as a algorithm that gets smarter over time.

Essentially it takes a distribution of a bunch of variables, randomly selects a value from each distribution, runs some sort of equation or algorithm using these random values, captures the result of the iteration, and then repeats this process many thousand times (5-10k times is typical).

Keep in mind appraisals are not done by algorithms but by humans and you could get a different number from 3 different appraisers.

Then it was LinkedIn and now Indeed is the most popular and you hear all sorts of fun about predictive algorithms telling people what candidates are going to the best and/or most interested in your open position.