A one way light switch is a switch that only has two connections (and an earth connection). These are L1 and COM. This switch is used on its own to switch a light or lighting circuit on and off. It cannot be used in conjunction with other switches, such as a two way or intermediate light switch.
A two way light switch can also be used as a one way switch. This means two way lights switches are more readily available. Many manufacturers and suppliers (including us) only stock two way light switches as there is very little difference in price between the two types of switch, and the two way switches are far more versatile.