T he time expression just expresses the time in seconds. For example, we can write an expression for position using the index: ,position,index*5] which means that x and y are normal, and then the z position is controlled by the index times 5. It's good for creating 3d ensembles and patterns. I f you duplicate the layer, it creates a duplicate in z space. For example, we can write an expression for position using the index: ,position,index*5] which means that x and y are normal, and then the z positionis controlled by the index times 5. If the layer is moved at the bottom, then the value would be the number of this last layer.
If the number of the layer is 3, then the index expressions added on a property of that layer returns avalue of 3.
The index expression just gives you the number of the layer. The random expression generates random values, like for example random(0,720), which randomizes the property of the layer (position, scale, rotation etc) between 0 and 720 every single frame. There are a lot of other useful expressions that we could use to make work a lot easier, such as the random, the index, and the time expressions.
