JSP stands for Java Server Pages. It means to embed Java code in HTML which can be done with the use of XML tags. JSP is used to add content to pages dynamically and helps in sending Java to the browser in a convenient manner.

Less Functions
Most of the JSP functions are used just for controlling the flow. It does not contain any other features. In fact, you need to define your own tags with tag libraries. This makes this language of no use for writing a simple database-driven website quickly.

The advantage of JSP is that it provides the power of Java while addition of things to HTML pages. This is specially suited for big companies. JSP is more of a 'build your own programming language' kit rather than a language in itself.

Separating the Application Logic
JSP is best used for separation of your application's logic from the HTML. It is a minimal language for doing more than just turning the Java application's output into a web page. This helps you to write an entirely new website with the use of your existing application as back end. However, it is difficult to add new functions to the site unless you are well versed with Java.

However, you have to be very careful as the HTML code might start creeping into the Java application's output. This makes it very difficult to write the JSPs and you may end up with broken web pages.

Use of Java
JSP's advantage is that it makes it easy to add Java applets to web pages. But Java is not considered a good option because it takes a long time to load and it doesn't offer anything that cannot be done with the use of Flash or HTML.

However, Java is more useful of servers if programmed in a correct manner. It is standardized and performs all possible functions.

JSP or ASP?
JSP serves as an alternative to Microsoft's ASP. ASP has the simplicity of Visual Basic whereas JSP has Java's power. ASP limits you to Microsoft's platform whereas JSP lets you explore any operating system you have that makes the use of Java.

Use by small websites
There are two groups of people when it comes to the owner of small websites. First, those who run their entire systems on Microsoft or Macromedia products as it save time and other who use languages such as PHP as it saves money and is appreciated more. In both these groups, there is not much room for JSP. Hence, small websites generally avoid JSP.