A particle physics dictionary can sometimes be a good idea.
- Dark matter can be understood simply as a bunch of heavy particles filling about 22% of the mass of the Universe. Dark matter is not distributed homogeneously in the Universe. It was introduced, historically, to explain the flat rotation curves of spiral galaxies. We know now that dark matter and energy are both needed to explain structures larger than galaxies and even the very origin of the Universe per se, the Big Bang.
- Dark energy is pure distributed pressure. Imagine somebody inflating a balloon. Dark energy inflates our Universe in a similar way. It is a substance homogeneously distributed not only in space but also in time meaning that its effects are not diluted as the Universe expands.
- Antimatter: An example of antimatter is the antielectron known as the “positron”. The positron is a particle identical to the electron except for its electric charge, which is opposite. If an electron and a positron meet each other they disappear in a burst of energy released in the form of pure light radiation.
- Standard Model is the ensemble of physical laws describing, at the fundamental level, all the chemical reactions and nuclear interactions.