The fish in the picture is Aplocheilus lineatus (striped panchax killifish). It is a gold form.
Males have longer more pointed dorsal (top) and anal (bottom) fins.
Males get bigger than females.
Males are more brightly/ intensely coloured than females.
When breeding, the male will swim near a female and flare its fins out and his colour usually gets brighter. He will entice her to some plants and the pr will go into the plants and swim next to each other. They will stop, shimmer/ shake for a few seconds and then swim out of the plants. That 2 seconds of shimmering is them releasing their gametes (eggs & sperm).
The eggs stick to plants and take about a week to hatch. The babies swim just under the surface and eat infusoria and other tiny bits of food. After a couple of weeks the fry can eat newly hatched brineshrimp.
The adult fish will eat the young so you should feed the adults really well when they are breeding and try to remove any fry to a separate tank.