What's the differences for slang, idiom and expression?

[snaren]

In my teaching i am not very familar with the word 'slang, idiom and expression' So could you give me the differences for each one with a very example to identify them?

[Kimlong]

Welcom Naren!!

How was your weekend! Did you join the official vote last day?

Anyway, let me share my understanding about your wonder of "slang, idiom and expression"

*Slang is a word that is not generally recognized. I mean it is used in a very specific location.If you say slang word to the one who doesn't live in that area, he will not understand what you say,(always informal). See here: http://www.slangsite.com/

*Idiom is word that is not literally used. It means that when we use it, its meaning changes from the original one. Ex: Hit the nail on the head = abosolutely right, rain cats and dogs= rain heavily, be over the moon=very happy, on the go with sth= very busy with sth....

For more see here: http://eslcafe.com/idioms/id-mngs.html

*Expression is word or phrase that is used to express about sth, include idioms. Ex: Wow means we feel shock or exited of sth...

For more  see here: http://en.wikipedia.org/wiki/Expression

Kimlong

[monivanc]

HI
i just want to ask that ''idiom is mostly use in native english speaking or not?''