The parenthesis '(' and ')' serve different functions depending on where they are used. The most common example I can think of is to group commands or statements together. Take the following example:
if ERRORLEVEL 1 (echo There was an error.
echo The ERRORLEVEL is %errorlevel%.
goto :EOF) else echo There was not an error.
Typically, when a batch file processes an IF statement, and the IF statement is TRUE, then it will excute 1 command on the same line as the IF. Since we have 3 statements surrounded in the parenthesis, it will group them together and execute all 3.
Compare to:
if ERRORLEVEL 1 echo There was an error.
echo The ERRORLEVEL is %errorlevel%.
goto :EOF
In the 2nd example, the last 2 lines of code get executed even when the IF statement is FALSE.
Does that explain it?