Just to be clear, "Cassini" is the name of the search engine... It is driven by computer program code (instructions). That code implements algorithm(s) which are processes to accomplish the work.
The algorithm of adding numbers together to find a total is called "Summation." The operator used to perform the summation is the addition operator, aka: "t=n+n" whereby 'n' is input data, t is output data.
Algorithms in computer science are simply processes, we can put whatever name on them we like.
Here's an algorithm I just made called "Froggy Doggy."
x=((14+c2) x (f4 - x3) x 5)
It add's 14 to a variable named c2 multiplying the result by variable f4 minus the variable x3 and then multiplies that result times 5 and assigns it to variable x. What's it do? Well I just told you! But lets say it computes a trajectory stone graphics in a video game or perhaps its how many "Hit points" you're dungeon and dragons character inflicts upon another character.
In the end, algorithms are processes of accomplishing work.
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The above is a data structure known as a "Binary Tree." There are algorithms to process binary tree's, this one is an "unordered" Binary Tree. The below is the result of running an algorithm over the unordered binary tree to "order" it. Now that it's ordered if we'd care find a value within the tree there are algorithms to "traverse" the tree following either right or left nodes depending on an algorithm comparing our input data against the data in the tree in ever so simplest of terms.
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