Originally Posted by your_shadow03
Can anyone explain me what that means?
That's a very vague question.
The answer Colucix posted is probably the best answer for such a vague question. But if you explain what you're really after, you might get a better answer.
Intel CPU model names, such as "Core 2 Duo" usually tell you very little about your CPU. The model ID's such as "T5800" tell you quite a lot (after you find some pages on Intel's web site, such as the one Colucix found, to tell you what "T5800" means).
Re, the subject line of your thread "My CPU architecture?
", your CPU supports two different architectures: X86 and X86_64.
flag Colucix mentioned is the most reliable indication that your CPU supports X86_64 architecture. That Intel web page also indicates all T5800's have "EM64T" which is Intel's name for X86_64. So that should also be a reliable indication.
Any CPU that supports X86_64 architecture also supports X86 architecture (that is part of the spec of X86_64).
So your installed Linux might be X86 or it might be X86_64 (you could find out with uname -a