The phrase "system planets" refers to the planets that orbit a particular star, just like how Earth orbits the Sun. It is used to talk about all the planets that belong to a specific solar system. Full definition
Through researching on my own and ignoring the vast consensus, I have made fantastic strides in understanding the whole system our planet has generated. (judithcurry.com)
Io remains volcanically active for a different reason — Jupiter and the moons Europa and Ganymede constantly tug on it — but the current eruptions on Io are likely similar to those that shaped the surfaces of inner solar system planets such as Earth and Venus in their youth. (keckobservatory.org)
Studying the climates of well - observed Solar System planets provides the necessary foundation for understanding habitability of exoplanets for which there will be less detailed information. (giss.nasa.gov)