hi

1)can anybody tell me what's the difference between I386 and X86_64.
2)where can i find RHEL workstation edition 5.5

Hello and welcome to LQ!

First, your query is not urgent. Please do not get into a habit of putting "urgent" into your thread titles - it will not work in your favor.

Now..

1) i386 and x86_64 both imply a machine architecture descended from the original Intel 8086-based platform, usually shortened to "x86" where x can be 2,3,4,5 or 6, with the higher numbers indicating more recent versions of the architecture. They are all 32bit. x86_64 means the same as above as far as the "descendants of Intel 8086 platform", but it is a 64bit architecture rather than 32. Google can direct you easily to some excellent and concise articles on this subject, particularly on Wikipedia.

2) As for RHEL of any variety, go to the RH website (I don't know the address off-hand). There, you can subscribe to, pay for, purchase, etc., all things RHEL. RHEL is not a free distro - to use it effectively, you need a paid subscription in order to access the software repositories, update your system, etc. Any version you might find for download somewhere, is probably not legal, and certainly won't be secure or up to date for very long. The RH website sometimes offers free BETA or TRIAL versions of their various offerings, and can certainly point you to any place you need to go to, to get RH products.

Cheers.
If you want to learn with a Linux distro that is just like RH, only not, then try CentOS.

https://access.redhat.com/downloads/ is where you can find RHEL 5.5, even to download the 30 day evaluation, you will require signing up. If you wanted free, then go with CentOS as GrepefuiTgirl said, it's compiled from the same source code as RHEL, but is freely available (and does not have any official support, which is what you're paying for with RHEL).

For bare bone user experience, on purely users lever, there's no difference. These two are different under the hood, not for your user related tasks. If your machine is 64-bit hardware, having 64-bit system on it, may result (if all other programs commit to this 64-bit mode) in better memory utilization and as a result in better performance. 64-bit will not work on 32-bit machines.

There are CentOS (which is binary twin brother of RH) and Fedora (current 13), which do everything RH does, using same tools and same ways. I personally prefer Fedora as to my opinion it is by far the best Linux distro. It also brings an extra benefit of useful learning, as all that you do there is directly convertible to Red Hat. Many these days use Ubuntu, but been Debian's family, it is not as much popular with large businesses. Red Hat along with somewhat SUSE are most widely used. Check out UnixAcademy.com , you will find there plenty of distros , training, exams etc. In general people change the distros a lot in a beginning. This way you develop "personal relationship" with some Linux clone, and stay with it for a while.

Off the subject or is it most colleges have students using a enterprise edition of linux. Then from there they begin to learn the system then the 101 linux for mid terms is what is the deference between the i386 and a x86_64.
just a thought or is it google.