Under Databricks Compute and Worker nodes, we find different types of types as below

Standard_D4ds_v5 => 16 GB Memory, 4 Cores
Standard_D8ds_v5 => 32 GB Memory, 8 Cores

In Databricks, each node will have one executor. I have questions below

(1) How much memory will be allocated for each core?
(2) For any background process, will be any number of cores and its memory will be allocated?
(3) If there is any backrgound process happens then what are all those activities?