expression
thanks for your hard work; I appreciate your efforts
Casual expression of appreciation for someone's effort, often used by a superior to a subordinate or among peers. Can sound condescending if used toward a superior; お疲れさま is safer in many situations.
ご苦労さん、今日はもう上がっていいよ。
Thanks for your hard work; you can go home now.
ご苦労さん、手伝ってくれてありがとう。
Thanks for your effort, and thank you for helping.
お疲れさま is a safer, more neutral expression of appreciation for effort, usable toward superiors and in most situations. ご苦労さん is more casual and can imply a hierarchical relationship.
From ご (honorific prefix) + 苦労 (hardship, toil) + さん (suffix expressing familiarity or appreciation).