Linux special character usage, background command management

!! Repeat the previous command
The character repeats the previous command that begins with "character"
!num Install the history command sequence number execution command
!? ABC repeats the command that contains "ABC" Before
!-n repeating the last nth command

Firefox & command +& continue to execute commands in the background
Jobs view commands being executed in the background
BG 2 continues to run the command numbered 2 in the background
FG 2 continues to run the command with number 2 in the foreground
CTRL + Z pause a running command to view the status of the command in the background using jobs

Linux special character usage, background command management