What is mean $_ [duplicate]

Question

What is mean by $_ , It may used like this

mkdir testdirectory;cd $_

It will redirect to the new directory

testdirectory

if i use like this , echo $_

It shows

testdirectory

Which means previously created directory.Actually what it means, I don't know really

Answer 1

what it means, I don't know really

$_ means the last argument to the previous command.

Example:

echo "FOO" "BAR"
FOO BAR
echo $_
BAR

Read more here.