The Lambda-CDM model (ΛCDM or LCDM) is a Big Bang Cosmological model including Cold Dark Matter and a Cosmological Constant (Lambda or Λ). The cosmological constant provides an explanation for the universe's observed accelerating expansion. Dark Matter provides an explanation for the dynamics of galaxies and Galaxy Clusters that appear to have more gravitational attraction than their light can explain.
Other explanations for these phenomena are some as-yet-unrecognized behavior of Gravity or dynamics.
The model relates many observed phenomena to six apparently arbitrary parameters determinable from observation:
The cited parameter list may differ from the above, but in combination, they would be equivalent to the above through relations assumed by the model. For example, the Optical Depth to Reionization represents a measure of how long ago the EOR took place, which is also sometimes cited as a Redshift (Z ~ 11).
Cold Dark Matter (CDM)
Einstein-de Sitter Model
Epoch of Galaxy Formation
Redshift-angular Size Relation