Mishna
The tractate consists of five chapters. The number of mishnayot is according to the standard numbering; however, different versions split up the individual mishnayot or combine them and the chapter breaks may vary as well.
Chapter One (nine mishnayot) deals with the prohibition of trade with idolaters around their festival (so as not to be complicit in the festivity) and the items that are forbidden to be sold to idolaters (which is basically any item that the idolater is likely to offer in an idolatrous service or commit an immoral act with). Thus, the main commandment explored in the chapter is lifnei iver.
Chapter Two (seven mishnayot) deals with precautions against the violence and immorality of idolaters and the items that are forbidden/permitted to be bought from idolaters. These include categories of objects that may be by-products of idolatrous services as well as foods with a difficult to identify kashrut status.
Chapter Three (ten mishnayot) deals with the laws of various images/idols and the asherah (idolatrous tree). Thus, it details the distinctions between forbidden and permitted use of various aspects and states of idolatrous items.
Chapter Four (twelve mishnayot) deals with benefit from the auxiliary items of a markulis (a Roman deity consisting of a heap of stones whereby worship consisted of throwing stones and thus adding to the heap) and other idols, the nullification of an idol (effected by an idolater deliberately defacing his/her idol) and the laws detailing the prohibition of the use and benefit of Yayin Nesech.
Chapter Five (twelve mishnayot) continues detailing the prohibition of yayin nesech and the kashering of utensils used by idolaters.
Read more about this topic: Avodah Zarah