What does it mean that cystic structure containing linear echoes in left ovary?

It means that there is a fluid-filled sac (cyst) in the left ovary that has thin, straight lines (linear echoes) inside it. This could be a sign of a benign condition called a corpus luteum cyst, which is a small cyst that forms during ovulation and usually goes away on its own. However, it could also be a sign of a more serious condition, such as an ovarian tumor. To determine the cause of the cyst, your doctor may recommend further testing, such as an ultrasound or MRI scan.