Lebanon is part of the fertile crescent, one of the areas where agriculture and urban life developed somewhat before 4004 BCE when fundies think it all began. In ancient times it was the heart of the Phoenician civilisation, but has spent much of the last 2,500 years as part of a succession of Empires, Persian, Greek, Roman, Byzantine, Islamic, Ottoman and French.
It was one of the key battlegrounds of the crusades and has many crusader castles amongst its rich archaeological legacy.
In 1919 at the end of the first world war the Ottoman Empire was divided and what are now Lebanon and Syria were handed over to France as its Syrian mandate. When the French withdrew they divided the mandate into two, Syria the larger part and overwhelmingly Muslim state, and Lebanon where a large proportion of the population were Christian Arabs.
Lebanese history since independence has been dominated by events to the south of it in Israel. As a result of the wars that created Israel the Lebanon has a large number of Palestinian refugees who Israel will not allow to return to parts of Palestine that are now Israeli. These refugee camps were for some years a stronghold of the PLO and a factor in the religious tension with Lebanon that lead to the Lebanese Civil war.
For much of the civil war Israel was seen to be in concert with certain Christian groups. All sides are alleged to have funded their arms by drug growing, principally Opium poppies for Heroin. The worst atrocities of the war were generally reckoned to be massacres of Palestinian civilians in the Sabra and Chattilah refugee camps, but every faction plus both Israel and the USA committed terrorist acts such as bombing or shelling civilian targets at some point in the war.
Lebanon has been invaded and parts of its country occupied by both Israel and Syria, though both have now withdrawn.
The Lebanese tend to identify themselves by religion more than any other factor, the chief divide is between the formerly dominant Christians and the now majority Muslims with also a significant Druze minority. But the Muslims are themselves divided between Sunni and Shia. Amongst the Christians Maronites are by far the largest group but there are several others.
Lebanon is a multiparty democracy, but Politics invariably follows religious lines and Lebanon has a complex compromise set up that reserves various roles for various religious Groups. Lebanon is one of the few middle east nation to have some limited  sort of Gay rights.