"Hyperechoic" is a term Radiologists use to describe regions in an ultrasound where echoes are stronger than they should be, or are stronger than the regions surrounding them.
An ultrasound machine works in a way that is similar to how a bat can fly in the dark. The ultrasound machine sends out sounds at very high frequencies. These sounds bounce off of different materials at different speeds, and then return to the ultrasound machine. The machine takes the difference in the time it takes for each sound to bounce back to produce an image that doctors can see. Hyperechoic foci, (foci means region or area) is a spot where the sounds bounced back faster than they would if they had hit normal tissue--in this case, normal ovaries.
So what does it mean that you have two small hyperechoic foci in your left ovary? A number of things can cause this. Sometimes small tumors will begin to grow on the ovaries, especially as a woman gets older. These tumors are usually harmless, and don't cause any problems. However, sometimes they can be cancerous, or be a growth of tissue that has left its proper place in the body. A common example is endometriosis, where tissue that should be in the uterus leaves and begins growing in other parts of the body.
It is impossible from the ultrasound itself to determine what the two hyperechoic foci are. This will require your doctors to obtain a complete history and physical from you, and may require them to get a CT or MRI scan or take a sample of the tissue and analyze it under a microscope. If it turns out to be nothing worrisome, then they will simply leave your ovaries alone. However, if they detect a problem, surgery will likely be required to remove your ovary.