Mode of execution of code matters
Every line of code that you write is executed to produce some result. But how this line of code is executed differs between programming and scripting languages. If code written in a language needs to undergo a process called compilation before it can be executed, then the language is a programming language. On the other hand, if code written in a language can be executed on the go and does not need any pre-processing, then the language is a scripting language.
Who is a client?
So, generally speaking, a client is someone in need of a particular service. When it comes to the web, people want to look up something or they wish to play a game, or shop online, and what not. As a person, one needs some software to act on their behalf. This is usually the web browser. Some of the commonly known and used web browsers are Mozilla Firefox, Internet Explorer, and Google Chrome.
What is a web server?
There are lots of clients out there seeking some service or the other. So, there has to be some people serving these clients, is it not? This is done by special computers called Servers. These servers operate at great speeds and are capable of handling multiple clients at the same time. If too many clients tend to crowd the server at the same time, then the server takes longer to service each and every client than usual.
So, a client wants service and server offers service.
So, what are websites and web applications then?
A website is a set of pages that are put on a particular server. These pages may have content that may or may not change. They do not do much other than displaying information they have been created for.
A web application is capable of doing something for the client. When one needs to shop, the online store needs to know what you are shopping and dispatch the items after you pay for them. There are online ticket reservation systems too. All these are present on the web offering some sort of service to the client.
Websites and web applications reside on the web server
So, these web applications and websites are served by the web server to the web browser. Many websites and web applications may reside on a single server or the server may be dedicated for a single one.