d no final de alguns processos significa daemon .
Deamon significa processos que funcionam em segundo plano e serviços funcionam em segundo plano.
Antecedentes aqui significa que você não tem acesso direto a eles e eles não estão esperando por você! Se você definir que um serviço aparece após a inicialização do sistema, ele será executado automaticamente.
Um pouco mais tecnicamente:
Daemons are usually instantiated as processes. A process is an executing (i.e., running) instance of a program. Processes are managed by the kernel (i.e., the core of the operating system), which assigns each a unique process identification number (PID).
There are three basic types of processes in Linux: interactive, batch and daemon. Interactive processes are run interactively by a user at the command line (i.e., all-text mode). Batch processes are submitted from a queue of processes and are not associated with the command line; they are well suited for performing recurring tasks when system usage is otherwise low.
Daemons are recognized by the system as any processes whose parent process has a PID of one, which always represents the process init. init is always the first process that is started when a Linux computer is booted up (i.e., started), and it remains on the system until the computer is turned off. init adopts any process whose parent process dies (i.e., terminates) without waiting for the child process's status. Thus, the common method for launching a daemon involves forking (i.e., dividing) once or twice, and making the parent (and grandparent) processes die while the child (or grandchild) process begins performing its normal function.
Duas boas referências: