Sraddha refers to a ceremony performed on behalf of the departed ancestors.
As a planetary combination, sraddha yoga is formed when Saturn joins one of the nodes, Rahu or Ketu. This combination implies that the last rights of one of the parents/ancestors were not performed/completed in the last birth, and the mourning period continues into this life, hence the name.
As a result, a person will experience suffering due to this ancestral karma.
Discover more about the Rahu & Ketu and various yogas, including nodes, here.