If you just missed the amazing part: it runs on your machine. How can a program from an unknown source be trusted to run on your computer without your permission? It can't unless that program was created using a secure language like Java, and then wrapped with a secure viewing browser like Netscape Navigator. The concept of being able to run applications on your system is significant for several reasons. If you want to see a picture, but don't have a picture viewer, you can get both at once. This eliminates the problem of not having the correct helper application or even worse: having to settle for what's available. The ability to run applications on your system has another significant advantage. Traditionally when you view something that "runs" on a Web page, or is interactive, the work takes place on the remote computer, not yours. Java frees Internet resources, allowing the work to take place on the client's system rather than the server's.
If all applications were run on remote computers, the servers would be inundated with traffic, and these collectively would propagate to bring the entire Internet to a grinding halt. With a growing Internet population, the prospect of this is real. There is a better way. If it can be done safely, isn't it quicker, not to mention more considerate, to get what you need, take it with you, and use it on your time? A good analogy is a long bank queue, with everyone waiting for the person in front of them to finish. Some will be quick, and others will attempt a hostile takeover on your lunch hour. Imagine a different world where tellers were issued at the bank. Instead of waiting for a teller to become free, you could simply take the teller you require from an almost endless supply, then complete your transaction without delaying the people behind you. You would only have to wait in line to get a teller. If the bank got hundreds of new customers every day, would there be any other way to do it? The issue of security would still have to be addressed.
