You need it for certain websites to work. These days admittedly not so many. Some crossword websites use java applets to display interactive crossword grids for example. Chat rooms are another popular application for them. My advice would be don't install it unless you hit a website that tells you you need java installed in order for it to work.
I don't know Emmie but, like you, I have those pop ups and then a flashing icon in the bottom left tray. I just do a restart and it disappears. I, like you, would like to know what it's all about though.
It's a programming language fundamentally. But the implications for you as a browser user are that some web pages use java applets (small embedded java programmes) . Because to run web java programmes you need to have something called an interpreter on your computer, you therefore have to have it downloaded from the official java site.
Beware however; some malicious websites take advantage of this by trying to fool you into downloading what appears to be java but is actually malware.
The pop up box is probably Windows warning you that something is about to install. It gives you the chance to think twice about whether you really want to install whatever it has downloaded.
You need it for certain websites to work. These days admittedly not so many. Some crossword websites use java applets to display interactive crossword grids for example. Chat rooms are another popular application for them. My advice would be don't install it unless you hit a website that tells you you need java installed in order for it to work.