Screws are more useful than nails when you need to secure wood together. Their large thread allows them to hold the timber tightly and when used with PVA glue the timber or joint is almost inseparable.
The countersunk head is usually the most common type used because its unique head allows it to be inserted below the timber’s surface and sometimes it is covered with a dowel to create a feature.
This head is also easy to use because its head helps to guide the component down. A hole should be pre-drilled first though to ensure it stays straight and to prevent the timber from splitting.