Difference between a URL and a URI

Uniform resource identifier (URI) and Uniform resource locator (URL) these two terms describes different concepts. 
A URI is used to identify something or perticular thing on the World Wide Web.
There are two types of URIs:

• Uniform Resource Name (URN): URNs basically state what something is, but do not have information on how to access it.
• Uniform Resource Locator (URL): URLs contain the location of something and tell the client program (usually a browser) how to access it.

Simply put, a URN is the name of something and the URL is the name and address. 

For example, the URL http://www.abcd.com/example1.html tells your browser that a file called example1.html can be accessed through the example domain using the HyperText Transfer Protocol (HTTP). This means that your browser is request that file and display it for you using HTTP.

A URL is a type of URI, along with URNs. Most people will never have to worry about calling a URL a URI by mistake. In fact, in most cases they will be correct in the same way as someone calling a poodle a dog is correct. For people involved in the actual coding of applications, however, the difference is important because not every URI is a URL (just as not every dog is a poodle).

What is "Big Data" means topic for IT field

Big data is a term used to describe the voluminous(Occupying or containing much space; large in volume, in particular )amount of unstructured and semi-structured data a company organization  creates -- data that  takes too much of time and cost to load  a relational database for analysis and implement. Although Big data is not refer to specific quantity of data.

Moto for looking at big data is to discover and invent repeatable business patterns. It’s mainly accepted that unstructured data, most of it located in text files and we all know what is text file is , accounts for at least 80% of an organization’s data. If left unmanaged, the sheer(extra ordinary)  volume of unstructured data that is generated  yearly within an enterprise or organization  can be costly in terms of storage of Data. Unmanaged data can also pose a liability if information cannot be located.

Big data is often associated with cloud computing because the analysis of large data world  in real-time requires a framework like MapReduce to distribute the work among tens, hundreds or even thousands of computers.