Particles can also be given custom properties, which can then be queried again in Conditions, in Math or Data Mapper modifiers, for example, or offset against other properties of the particle. The Basic Emitter offers two properties for storage.

To use the corresponding storage, activate the option to the right of its name. A new custom property whose data type is compatible with the output value is automatically created and entered. These automatically generated custom properties are stored within the Scene Settings and their Particle Simulation Settings in the group for Automatic Custom Properties section.
However, you can also go to the group for Manual Custom Properties and manually create your custom properties there by yourself. You will find an arrow button behind the respective name field of the Output properties, which can be used to open a selection list of the available custom properties. These lists are automatically filtered to display only the custom properties of the simulation scene whose data types are compatible with the Output value.

You can find out more about the manual creation of custom properties for saving and processing particle properties in the section on Particle Simulation Settings within the Scene Settings.

Born

This bool information indicates with the value true if a particle has just been created. For subsequent images, the value should be automatically reset to false in order to only mark newly created particles with true. For this to work, a custom property of the Event Bool type must be assigned here. Activating the Born option automatically takes care of this. Alternatively, you can click on the arrow button next to the name field to select one of your manually created custom properties that also uses this data type.

UVW Coordinates

Vectors are output here to describe the UVW coordinates of the point on the emitter where the particle was created. Please note that the W component is only used for the 3D shapes of the emitter. With the two-dimensional emitter shapes, only the U and V components are changed and the W component remains constant 0.
Activating the UVW Coordinates option automatically creates a custom property with a suitable Vector data type. Alternatively, you can click on the arrow button next to the name field to select one of your manually created custom properties that also uses this data type.