These are blocks that provide data (for example a temperature sensor).The variables present 2 blocks, a Get and a Set block.  

The Get block can be used as a condition on a runtime. An example is this Alarm Routine where roomTemp get is used as a trigger for the alarm.

The Set block is used to write  a value following meeting a condition, which can be a block or an entire routine. It can also be used as a condition on itself

Like variables, variable blocks are color-coded by type as follows:

Number - Purple

Boolean - Green

String - Gold

Time/Date -Teal