Iso - it's an image of CD or DVD discs on your games, you can make those using nero, Alcohol 120%, DVD Decrypter, CloneCD and many othere programs, files with ELF extentions are programs for PS2, something like files with *.exe extention for PC.
If you want ISOs you should make them from your bought games, and ELFs... probably you are thinking about homebrew programs for PS2, those are in the internet, to run them your PS2 must be able to run backups (eg. by using swap trick or installing modchip) which is in gray area and because of that we are not allowed to talk about it.
Also talking about getting isos, bioses and such is prohibited on this forum.
If you haven't read [rules]Rules[/rules] I sugest you to do that. Reading FAQs can help also.
If you want ISOs you should make them from your bought games, and ELFs... probably you are thinking about homebrew programs for PS2, those are in the internet, to run them your PS2 must be able to run backups (eg. by using swap trick or installing modchip) which is in gray area and because of that we are not allowed to talk about it.
Also talking about getting isos, bioses and such is prohibited on this forum.
If you haven't read [rules]Rules[/rules] I sugest you to do that. Reading FAQs can help also.