Can I create a group of tiles using an app that is not installed in the system? Like eclipse is just an executable I launched in win7. Also where is windows explorer??
yes you can pin any kind of application to the start screen. And windows explorer has been renamed to file explorer. You can just search for it from the start screen (just type). And it should be pinned the taskbar as well. Also if you just want an all applications list, just right click on the start screen and click in the lower right corner.
But basically, use search. Where is Device Manager? Type device manager on the start screen and filter by settings. How do I change my mouse speed? Type mouse speed on the start screen and filter by settings. Where is notepad? type notepad on the startscreen and hit enter (default search is applications). Want to update your drivers? Type drivers on the startscreen and filter by settings. Looking for a certain file? type it in on the start screen and filter by file. Want to search the music app for a song? type it into the start screen and changet he filter to the music app. Want to search the web? type it into the start screen and filter it using the IE app, the bing app, the google app etc... You get the idea. You don't need to look through menus to find stuff, just search for it. (I have been doing this since vista, i'm amazed more people don't do this). Search has been a very powerful function in windows for awhile, and 8 has improved it a lot. (well some people don't like that apps, settings and files are separated but whatever). The ability to search within these new applications is awesome. very useful.
and since the startscreen can be accessed with the windows key, its the same as vista and 7 when on the desktop. Win Key + Start Typing.