Final answer:
Detected extrasolar planets commonly have masses similar to Jovian planets due to observational biases, but super-Earths and mini-Neptunes are also significant, and smaller terrestrial-like planets are actually thought to be more common.
Step-by-step explanation:
Most of the extrasolar planets detected to date tend to have masses that are more similar to Jovian planets, meaning they are closer to the mass of the gas giants in our solar system like Jupiter and Saturn, rather than terrestrial (Earth-like) planets. This is largely due to an observational bias, as larger planets are easier to detect using methods such as the Doppler and transit techniques. Over time, and especially due to the missions like Kepler, the population of detected exoplanets now includes many that are known as super-Earths and mini-Neptunes, which do not have analogs in our solar system. Super-Earths are rocky planets with masses between two to ten times that of Earth, while mini-Neptunes are larger than Earth but smaller than Neptune. Despite these findings, smaller planets like the terrestrial planets in our system are thought to be more common than giant planets when taking these selection biases into account.