What is the difference between $(command) and `command` in shell programming?

What is the difference between $(command) and `command` in shell programming?

bash shell ksh sh

bash

Select unique or distinct values from a list in UNIX shell script

bash unique distinct ksh sh

bash

How to detect if a script is being sourced

bash ksh

bash

What does it mean in shell when we put a command inside dollar sign and parentheses: $(command)

bash shell terminal sh ksh

bash

Grab the filename in Unix out of full path

bash shell unix ksh

bash

Get exit code for command in bash/ksh

bash unix ksh exit

bash

Find all files in a directory that are not directories themselves

bash unix ksh

bash

Is it necessary to specify traps other than EXIT?

bash shell ksh zsh sh

bash

How do I recursively list all directories at a location, breadth-first?

linux bash shell ksh

bash

Shell script templates [closed]

bash unix scripting standards ksh

bash

How to expand shell variables in a text file?

bash shell unix solaris ksh

bash

how to get day of the year in shell?

linux bash shell ksh

bash

File execution with dot space versus dot slash

linux bash shell operators ksh

bash

set -e and short tests

bash shell ksh zsh

bash

Why does `if $(true) ; then ... fi` succeed?

bash ksh zsh sh

bash