This function is used to create a new particle system and will return a unique index number that should be stored and used in all further functions relating to that system. The system will be assigned a managed layer and will be set to have a depth of 0. Managed layers are not accessible to the user and used only for internal management when depth is used instead of layers. Normally you would use the function part_system_create_layer instead of this one.
global.Sname = part_system_create();
This will create a new particle system and store the index in the global variable "Sname".