What is the meaning of groundwork?

noun

• The fundamental assumptions from which something is begun or developed or calculated or explained.
  • usage: "the whole argument rested on a basis of conjecture"
  • synonyms: basis, base, foundation, fundament, cornerstone
• Lowest support of a structure.
  • usage: "it was built on a base of solid rock"; "he stood at the foot of the tower"
  • synonyms: foundation, base, fundament, foot, substructure, understructure
• Preliminary preparation as a basis or foundation.
  • usage: "we are prepared today because of groundwork that was done ten years ago"