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A pleural effusion is a fluid buildup between the tissue layers that line the lungs and chest cavity. Your body produces pleural fluid that surrounds the pleura. The pleura are thin tissues containing this fluid that surround the lungs and inside of the chest cavity.

There are two kinds:
There are two types of pleural effusion: https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/pleural-effusion#:~:text=A%20pleural%20effusion%20is%20a,the%20lungs%20and%20chest%20cavity.

Transudative pleural effusion is caused by fluid leaking into the pleural space. This is from increased pressure in the blood vessels or a low blood protein count. Heart failure is the most common cause.
Exudative effusion is caused by blocked blood vessels or lymph vessels, inflammation, infection, lung injury, or tumors.

I suggest that you call your doctor so that you can be treated. Your symptoms are consistent with pleural effusion but that doesn't mean that is what caused your coughing up blood.