Answer what is running and why.

ps

Everything, wide enough to read

ps auxww

Find a process by name fragment

ps aux | grep -v grep | grep '[n]ode'

The bracket trick stops grep from matching its own command line.

What is using memory right now

ps -eo pid,comm,rss --sort=-rss | head

Threads of one process

ps -T -p <pid> -o pid,tid,comm

Scope: ps