can anyone explain about web APP?
From a technical view-point, the web is a highly programmable environment that allows mass customization through the immediate deployment of a large and diverse range of applications, to millions of global users. Two important components of a modern website are flexible web browsers and web applications; both available to all and sundry at no expense.
Web browsers are software applications that allow users to retrieve data and interact with content located on web pages within a website.
Today’s websites are a far cry from the static text and graphics showcases of the early and mid-nineties: modern web pages allow personalized dynamic content to be pulled down by users according to individual preferences and settings. Furthermore, web pages may also run client-side scripts that “change” the Internet browser into an interface for such applications as web mail and interactive mapping software (e.g., Yahoo Mail and Google Maps).
Most importantly, modern web sites allow the capture, processing, storage and transmission of sensitive customer data (e.g., personal details, credit card numbers, social security information, etc.) for immediate and recurrent use. And, this is done through web applications. Such features as webmail, login pages, support and product request forms, shopping carts and content management systems, shape modern websites and provide businesses with the means necessary to communicate with prospects and customers. These are all common examples of web applications.
Web applications are, therefore, computer programs allowing website visitors to submit and retrieve data to/from a database over the Internet using their preferred web browser. The data is then presented to the user within their browser as information is generated dynamically (in a specific format, e.g. in HTML using CSS) by the web application through a web server.
How do web applications work?
The figure below details the three-layered web application model. The first layer is normally a web browser or the user interface; the second layer is the dynamic content generation technology tool such as Java servlets (JSP) or Active Server Pages (ASP), and the third layer is the database containing content (e.g., news) and customer data (e.g., usernames and passwords, social security numbers and credit card details).
The figure below shows how the initial request is triggered by the user through the browser over the Internet to the web application server. The web application accesses the databases servers to perform the requested task updating and retrieving the information lying within the database. The web application then presents the information to the user through the browser.