Basic solder terminals are turned, usually from brass, in a variety of forms. Each part has some means of retention in the board. This is usually either a knurl or a drilled hole in the base which allows the shank of the terminal to be rolled over or swaged after passing through the board, the diameter shank is passed through the board and swaged. The swaging tool passes over the bottom terminal to swage the terminal.

Some terminals are formed from brass tube which reduces the weight of the part also the hole may be used as an additional wire termination point. 

To view datasheets on Eyelet type, non insulated solder terminal, swage mount

http://www.cambion.co.uk/Main/eyelet.htm