Programming

hello
let me start with
i am a php ,vb ,c# programmer
i heared that Routers run a smaller version of linux called an Embedded Operating System
i don't know what is that mean
so i want to know how to get into router files ?
how to edit it ?
what language it use , is it c and c++ ?

i just need to know how to start i mean if some one ask me how to start with php or vb or i want to edit vBulletin or any thing use php

i would give him a link to download any loacl server , editor
and tell him how to write the first code like
echo "hello world";
and after that could tell him more about this language
until he/she became an professional then he will be able to edit it
that how i want to get an answer
in my case i didn't know where is the files
what is the language ,the editor
nothing

and please some one answer me without give me a alot of links to read
just tell me how to start by answer my questions and
thank you

There are more than two steps to this process you dont go from "hello world" to being a professional in one conversation. If your not willing to read any links then your out of luck.
Writing code for embedded linux is the same as writing code on a linux desktop just with less resources. If you've never written code on linux at all thats where you start.
Writing code for a router doesnt require a specific language. Its a type of computer not a type of language.
You wouldnt "get into the router files" if you want to write code to run on a router you would cross compile it. Aka Compile the program on one platform to run on another you wouldnt compile your code on the router.
openwrt is a linux distro for routers that you could write a program to run on.
Id link you to resources to learn how to do these things but you specifically asked not to be so use google.