There is no concept behind Ramadan! But there are a few facts on which Muslims believe in.
• There is a common misconception that Ramadan is special because Muslims are prescribed to fast in this month. However, this month is special because the Quran, the book revealed to Prophet Mohammad SAW, was revealed in this month.

"The month of Ramadhan [is that] in which was revealed the Qur'an, a guidance for the people and clear proofs of guidance and criterion. So whoever sights [the new moon of] the month, let him fast it; and whoever is ill or on a journey - then an equal number of other days. Allah intends for you ease and does not intend for you hardship and [wants] for you to complete the period and to glorify Allah for that [to] which He has guided you; and perhaps you will be grateful." [Chapter 2, Verse 185]
• Muslims fast in this month so that they can increase Taqwa, roughly translated as God fearing, in this month. We are trained in this month to stay away from permissible things like eating, drinking, sexual relations with spouses etc. during this month so that after this month it's easier for us to stay away from impermissible things like alcohol, fornication, gambling, lying, backbiting etc.

"O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous" [Chapter 2, Verse 183]