What is the difference between oligo polistic competition and pure monopolistic competition?

In monopolistic competition, firms capture monopoly profits through specialisation of their product, making it non-substitutable with competing firms' products. In oligopolistic competition, this does not occur. Instead, three are three general outcomes: 1) firms collude to mimic a monopoly and share monopoly profits; 2) a dominant firm leads the market and sets the price; 3) firms compete freely and but take each other's decisions into account.