yet another dumn question

[Angus Leeming]

Which is "better"?
        (cd ${DIRNAME}; ${FDESIGN} -convert ${FDFILE})
or
        (cd ${DIRNAME} && ${FDESIGN} -convert ${FDFILE})

        if [ $? -ne 0 ]; then
                echo "\"${FDESIGN} -convert ${FDFILE}\" failed. Please investigate."
                exit 1
        fi

I'm not used to the "&&" stuff. can someone explain to me just what it does? 
Ie, does it interrogate return values? If the first command fails, does it 
execute the second?

Angus