Complex sentence: Gliese 876 b is in a 2:1 orbital resonance with the inner planet Gliese 876 c. This leads to strong gravitational interactions between the two planets and as a result the orbital elements of the planet change fairly rapidly as the orbits precess.
Split into simpler sentences: Gliese 876 b is in a 2:1 orbital resonance with the inner planet Gliese 876 c, which leads to strong gravitational interactions between the two planets. Therefore the orbital elements of the planet change fairly rapidly as the orbits precess.