Honey flow is one of those confusing terms, especially to new beekeepers. What is flowing during a honey flow is actually nectar. Technically, it should be called a nectar flow.
A honey flow is simply a period of time when one or more species of nectar-producing flowers is in bloom and actively producing nectar. During these times, honey bees collect the nectar and bring it back to the hive to be processed into honey. A honey flow may or may not coincide with a “pollen flow”–another weird term since pollen isn’t liquid and doesn’t actually flow. Whether the bees are collecting only pollen or only nectar or both depends on what types of flowers are in bloom at any given moment. It will be different in every location.
Signs of a nectar flow in progress include the appearance of snow-white wax in the hives, bees that seem especially intent on coming and going without a lot of dorking around, and a hive that increases in weight daily. Once you develop an “eye” for honey bees, you can often see the distended abdomens of nectar-laden bees.