What does true and false commands do ?

commandline session

$true 
$true $?
$echo  $?
0
$false
$echo  $?
1
$echo  $?
0
$echo  $?
0
$false ; true
$echo  $?
0
$true ; false ; echo $?
1
$true ; false ; echo $?
1
$true ; false ; echo $?
1
$true ; false ; echo $? ; echo $?
1
0
$true ; false ; echo $? ; echo $?
1
0
$echo $?
0
$echo $@

$echo $@

$tru
true      truncate  trust     
$true 
$echo $@

$echo @
@
$