What does > nul 2>&1 mean in a batch statement

Question

I currently have a batch statement that looks like this

findstr "PreprocessorDefinitions=.*%D_KEYWORD%" %PROJ% > nul 2>&1
if errorlevel 1 (
    set D_OPT=
) else (
    set D_OPT=/D%D_KEYWORD%
)

I wanted to know what the following means ?

> nul 2>&1

I looked here and it states that

... >nul 2>nul

means ignore output of command and ignore error messages

Now my question is how can I modify this command

 findstr "PreprocessorDefinitions=.*%D_KEYWORD%" %PROJ% > nul 2>&1

to show everything and not to ignore the error messages