There are some very good articles out there that describe the Linux (Unix) filesystem layout and the purposes for each directory. One book that is great for learning is called
Running Linux (O'Reilly Press), it gives you all the basic fundamentals (and more) of the Linux operating system. However, I will attempt to describe some of the basics.
The linux filesystem is setup with directories and sub-directories, like Windows, except there are no "C:" or "D:" drives, etc. Instead, linux has what are called "mount points". Just picture this, rather then going into My Computer and seeing A:, C:, D:, E: for your floppy, hard disks and cd-rom's, you go into "C:cdrom" for your cdrom and "C:floppy" for your floppy. Moving into these folders would display nothing if there were no cdrom in the drive and so on.
The linux filesystem has a base directory called "/" (or root directory). This is the begining of everything. Beneath this directory there are sub-directories. The most basic are:
/ - The root filesystem, the begining of it all
/bin - Essential user command binaries (for all users)
/boot - Static files for booting up your system
/dev - Device files
/etc - System configuration files
/home - User home directories
/lib - Essential shared libraries/kernel modules
/mnt - Mount point for temporarily mounted filesystems
/opt - Addon application software packages
/root - Home directory for root user (administrator)
/sbin - System binaries
/tmp - Temporary files
/usr - Sharable read-only data, most software is installed here
/var -Variable data files such as logs, mail spools, etc.
Some of these you don't really need to think about until you really get into Linux, others are fundamental. The /home directory is where your own little userspace is. For example, on installation, your system should have asked you to set up a user, if you chose 'johnny' as your username, then it would have made a directory for you called "/home/johnny", this is your users home directory, while logged in as user, this is where you would be able to save stuff and use for whatever. As each user is added, they are given a directory under /home for themselves.
/dev contains any and every device that would be attached to your computer. For example, your hard-drive is most like the device /dev/hda and the second partition on your hard drive is /dev/hda2 . Your floppy drive is /dev/fd0 , while your cdrom may be /dev/hdb (most systems will link your cdrom to /dev/cdrom". Other devices like your mouse, joysticks, sound device are all stored in this directory. You shouldn't need to mess with anything in there, as most system set everything up for you.
/mnt directory is where your cdrom and floppy disks (among other things) are mounted to. For example, when you place a cd into your drive and you want to read something off it, you would issue the command (in console) "mount /mnt/cdrom". This will "mount" the cd to the directory /mnt/cdrom. Now you can just change into this directory (cd /mnt/cdrom) and view everything on the cd. Window managers like KDE or GNOME will create an icon on your desktop that will allow you to mount and unmount your cd's and floppy disks when you need them. Remember, when you are done with a cd and you would like to take it out, you must unmount it first ("umount /mnt/cdrom") or else your cd drawer won't open. You can mount other things in this directory as well, such as a Windows 98 partition that you have. If it's on the first partition on your hard drive, then you can mount it by creating a directory in /mnt (mkdir /mnt/win98) and mounting it with "mount -t vfat /dev/hda1 /mnt/win98". This will allow you to look at, and edit, anything on that drive.
In windows, when you install a software package, it usually installs in something like "C:Program FilesSoftware Package". In this directory you usually find the execuatble, configuration files, help documentation, etc, all in one place. Linux, on the other hand, has a specific place for each part of a package. Your binaries (executables) will probably be found in "/usr/local/bin" while your configuration files are in "/etc" and help documentation in "/usr/local/share/doc". (Note: These directories may differ depending on the package you install).
The /usr directory hosts all your software for your system 99% of the time (the other 1% you will find in either /opt or in your home directory).
To execute a program in linux, you can simply type out the name of the program from the command line, or click on the menu in KMenu or Gnome. Whenever a software package installs, it installs the binary (or executable) into a directorys (either /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/sbin or /usr/local/bin) and using a "Shell Variable" called PATH, linux knows where to look for the program if you just type it out. Unlike in windows where 99% of the time you have to go into the programs specific directory in order to run it.
Tip: IF you want to see how many programs are on your system, press your TAB key twice from console. The tab key is very useful for helping you speed up the location of programs, for example, if you want to run opera, you can type out "Ope" and press the TAB key twice and it will eithe rcomplete the name or give you anything that matches what you have typed. VERY useful.
Now, as for Opera, you should have downloaded the installation package with the extension "RPM": opera-6.11-20021129.3-shared-qt.i386.rpm . This can be isntalled by going into your console (or konsole if you're in KDE), and change to a root user and installing with the following commands:
QUOTE
su -
(enter root password here)
rpm -i opera-6.11-20021129.3-shared-qt.i386.rpm
su - allows you to change to root so you can have access to writing to anywhere on the system (regular users aren't allowed to write anywhere but their home directory and /tmp). The second command installs the package using the RPM (Redhat packaging Manager). After this completes, you can just close down your konsole and opera should be in your menu.
Any more questions, let me know

btw, what do you mean by "tick" ?