"Section 1983 Litigation" refers to lawsuits brought under Section 1983 (Civil action for deprivation of rights) of Title 42 of the United States Code (42 U.S.C. § 1983). Section 1983 provides an individual the right to sue state government employees and others acting "under color of state law" for civil rights violations. Section 1983 does not provide civil rights; it is a means to enforce civil rights that already exist.
Bivens action: Section 1983 only applies to local state governments. A “Bivens action” is the federal analog which comes from Bivens v. Six Unknown Named Agents of Federal Bureau of Narcotics, 403 U.S. 388 (1971). Subject to certain exceptions, victims of a violation of the Federal Constitution by a federal officer have a right under Bivens to recover damages against the officer in federal court despite the absence of any statutory basis for such a right.