Complex sentence: The boosters used on the GSLV-III will be the S-200, which is also designated Large Solid Booster, or LSB, which is a solid propellant stage with a mass of 200 tonnes.
Split into simpler sentences: The boosters used on the GSLV-III will be the S-200, which is also designated Large Solid Booster, or LSB. It is a solid propellant stage with a mass of 200 tonnes.