In sexually reproducing species offspring production depends on access to members (and gametes) of the other sex. This implies strong selective pressures acting upon multiple aspects of sexual interactions. In this talk I will revise some concepts, and I will discuss a few challenges and ways forward, in relation to the study of sexual selection. Polyandry (when females mate with multiple males) is a widespread behaviour with far-reaching implications. Polyandry typically leads to ejaculates from different males overlapping in the fertilization arena, thereby extending sexual selection beyond mating. By facilitating postcopulatory sexual selection, female multiple mating generates intense selection for male and female adaptations that allow individuals to gain control over paternity biases. Polyandry also enables the evolution of adaptations resulting from sexual conflict over mating frequency and paternity. I will mainly use results from my own work carried out over the last years to navigate through these questions, focusing on several aspects connected to them, including: bet-hedging as a mechanism underlying the evolution of polyandry, the interaction between ecology and mating system selection histories underlying sexual conflict dynamics, and some discussion on the transgenerational consequences of sexual interactions.