Java is a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day.
IIS is able to impersonate the IUSR_<computername> account because the user name and password for this account are known by IIS. Before returning a page to the client, IIS checks NTFS file and directory permissions to see if the IUSR_<computername> account is allowed access to the file.
Investopedia says: IRR Often used in capital budgeting, it's the interest rate that makes net present value of all cash flow equal zero. Essentially, this is the return that a company would earn if it expanded or invested in itself, rather than investing that money elsewhere.