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The Big Bang Theory is the leading cosmological model explaining the origin of the universe, postulating that it began from an extremely hot and dense singularity about 13.8 billion years ago and has been expanding ever since.

The CMB is the thermal radiation left over from the time of recombination in Big Bang cosmology, and provides strong evidence for the Big Bang Theory as it can be observed in all directions in space.

Baryonic matter is the 'ordinary' matter comprising protons, neutrons, and electrons, as opposed to dark matter and dark energy. Baryons make up all the physical objects in the universe, including stars, planets, and galaxies.

The Cosmological Principle is the assumption that on large scales, the properties of the universe are the same for all observers irrespective of their location or direction of observation. It underlies the models of the universe that are based on general relativity.

Cosmological redshift refers to the stretching of the light from distant galaxies due to the expansion of the universe, which serves as evidence for the Big Bang Theory.

A singularity in the context of the Big Bang Theory is the point at which density and temperature of the universe were infinite, considered the starting point of the universe.

Recombination is the epoch in the early universe when charged electrons and protons first combined to form neutral hydrogen atoms, allowing light to travel freely for the first time. This occurred approximately 380,000 years after the Big Bang.

Cosmic inflation is the theory that proposes a period of extremely rapid exponential expansion of the universe during its first few moments (i.e., fractions of a second after the Big Bang). This addresses several cosmological puzzles like the horizon and flatness problems.

Nucleosynthesis refers to the process of creating new atomic nuclei from pre-existing nucleons (protons and neutrons). Primordial nucleosynthesis is believed to have taken place in the first minutes after the Big Bang, responsible for forming most of the universe's helium, along with other light elements.

Dark energy is a hypothetical form of energy that permeates all of space and accelerates the expansion of the universe. It is estimated to contribute about 68% of the total energy in the observable universe.

Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe, and about a quarter of its total energy density. Its presence is implied by its gravitational effects on visible matter, radiation, and the large-scale structure of the universe.