Final answer:
Over 800 exoplanet systems have been discovered, implying at least a few thousand exoplanets, with Earth-sized planets being the most common in our galaxy.
Step-by-step explanation:
The number of exoplanets discovered to date falls into the category of a few thousand. By 2022, astronomers had identified over 800 exoplanet systems and estimated that there are at least 50 billion planets in our Galaxy alone. The data suggest that planets like Earth, which are smaller than the giant planets and sometimes categorized as 'super Earths,' are the most common, and that there may be around 100 billion Earth-size planets in the Milky Way. These discoveries have led to new perspectives on planet formation and challenged our conventional views, highlighting a diverse range of planetary system architectures.