SPST means single pole, single throw switches. This means that the switch connects the two pins in one position, and they're disconnected in the other.
SPDT (single pole, double throw) switches have 3 pins. In one position the centre pin will be connected to one outer pin, and in the other position it'll be connected to the other outer pin. You can use these in the same way as a SPST switch if you only use the middle pin and one of the outer pins.
An SPST 2 pin switch might well be labelled as on-on as they probably use the same metal parts for 2 pin and 3 pin switches, but if its only got two pins then only one position can possibly be on.
The switches you have don't have a centre position. They will be fine for any on/off switching you need to do.
The rapid site can be confusing in that all questions about any of the entire salecom miniature switch range will appear on the page for each individual switch. The questions and answers really should mention which specific switch they are referring to.