Life history evolution is central to evolutionary biology. It deals with the schedule of reproduction and mortality over lifetime and attempts to understand the variation in the timing and frequency of reproduction and allocation of energy to reproduction, growth and maintenance. In this teaching lecture, I will cover the fundamental aspects of life history theory, place it in the context of natural selection and discuss its scope. I will then consider the major life history traits: age and size at maturity, number and size of offspring, and reproductive life span and ageing. I will then explore life history strategies using insects as an example. Finally, I will discuss limitations and paradoxes associated with these concepts. This talk will aim to give a broad and conceptual introduction to the theoretical body of work dealing with the evolution of life histories.