ความรู้ภาษาอังกฤษของฉัน

Idiom: a manner of speaking that is natural to native speakers of a language

Every language has its own collection of wise sayings. They offer advice about how to live and also transfer some underlying ideas, principles and values of a given culture / society. These sayings are called "idioms" - or proverbs if they are longer. These combinations of words have (rarely complete sentences) a "figurative meaning" meaning, they basically work with "pictures".
This List of commonly used idioms and sayings (in everyday conversational English), can help to speak English by learning English idiomatic expressions. This is a list, which contains exactly 66 of the most commonly used idioms and their meaning.

A hot potato

Speak of an issue (mostly current) which many people are talking about and which is usually disputed

A penny for your thoughts

A way of asking what someone is thinking

Actions speak louder than words

People's intentions can be judged better by what they do than what they say.

Add insult to injury

To further a loss with mockery or indignity; to worsen an unfavorable situation.

An arm and a leg

Very expensive or costly. A large amount of money.

Source : http://www.smart-words.org/quotes-sayings/idioms-meaning.htmlhttp://www.smart-words.org/quotes-sayings/idioms-meaning.html