Through-hole components are electronic components that have pins that go through the board. And you solder them on the other side of the board. Through-hole components have been used in the electronics industry for many, many years. But they are becoming less and less used. Instead, surface-mount components are taking over instead. The reason for this is that surface mount components take less space and require a simpler soldering process. At least it’s simpler for machines to do it – not humans.
But sometimes, maybe it’s better to use through-hole components instead of surface mount components. For example, if you are making a product that you are planning to mass-produce, then it’s a better idea to use surface mount technology. It will be cheaper in the long run. But if you want to make your first blinking light, then stick to through-hole. As long as you don’t have any strict space or cost requirements, then use through-hole when possible. The reason we promote through-hole over surface mount, is mostly because their easier to solder.