PageRank algorithm

Google Algorithm is a link analysis algorithm, named after Larry Page and used by the Google search engine, that assign a numerical weighting to each element of a hyperlinked set of documents.

In short PageRank is a vote by all the other pages on the web and about how important page is. A link to a page is counts as a vote of support.

Equation of PageRank is......

Greedy algorithm

Greedy algorithm always makes the choice that look better at a brief period of time. i.e., it form a locally optimal choice in the hope that this choice will lead to globally optimal solution.

 The procedure is powerful and work in a good for wide range of problem.
An optimal problem is one in which you want to search, not only solution of problem, but better solution of a problem. Greedy algorithms works better for optimization problems.

A greedy algorithm works in different phases.
At each different phase:

You desire the better you can obtain right now, without consider for future result or effect.

You desire that by selecting a local optimum at every step, you will end up at global optimum.
Example: 

Suppose you want to count out a certain value of money, using the few possible bills and coins. A greedy algorithm would do this in the following steps:

To make $6.39, you can choice following coins

Algorithm

An Algorithm is well defined computational procedures that takes some values or set of values as an input and produce some values or set of values as output. Thus an algorithm is a set of computational procedure that transfer input to output. We can also views that algorithm is a tool for solving well-specifies computational problems.