First, isn't jre available using the package manager? (Always install SW using the package manager if possible.)
Second, if you get jre for Ubuntu, you don't want RPM (I don't remember all the options)
Finally, there are many kinds of installers, but there are some common principles:
1. If there is an extension like .tar, .gz, .bz2, etc. then you have to extract first.
2. A file ending in .bin is typically expected to be executed, but you often have to set the permissions first. Example--for your case:
3. Instructions are typically available where you got the file, or in something like a README file.
Going back to one of your original questions: Commands are sometimes run in directories that are not listed in the PATH variable. This means that the full path must be given. Suppose, for example, you have that file in /home/username/downloads. That directory would not normally be in PATH, so if you simply type the file name, the system does not know where to look. You can:
a. cd to the directory and enter " ./filename"
b. enter /home/username/downloads/filename