What Does This Ultrasound Thyroid Report Indicate?

This is my US thyroid report, can you please define it to me.There is a well defined isoechoic/solid lesion in the right lobe of the thyroid gland , 11 X 10 X 8mm and a smaller hypoechoie nodule in the left lobe measuring 3 x 4mm. There is no retrosternal extension of the thyroid gland or local lymphadenopathy.What is isoechoic , hypoechoic a retrosternal mean ?.thankyou