  This review provides an introduction to the radio emission by particle
cascades, an overview on the various experiments, and explains methods for the
radio measurement of air-shower properties. Furthermore, potential applications
of the radio technique in high-energy astroparticle physics are discussed. Due
to the successful operation of digital radio experiments and due to the
improved quantitative understanding of the emission, radio detection is back on
the list of promising techniques for extensive air showers. With a threshold of
about 100 PeV radio detectors are particularly useful to study the
highest-energy galactic cosmic rays and ultra-high-energy extragalactic
particles of all types. Various antenna arrays like LOPES, CODALEMA, AERA,
LOFAR, and Tunka-Rex have shown that radio measurements can compete in
precision with other techniques, in particular for the arrival direction, the
energy, and the position of the shower maximum. The scientific potential of the
radio technique seems to be maximum in combination with particle detectors,
which increases the total accuracy for air-shower measurements. This is crucial
for a better separation of different primary particles, like gamma-ray photons,
neutrinos, or different types of nuclei. In addition to air-showers the radio
technique can be used for particle cascades in dense media. Several pioneering
experiments like ARA, ARIANNA, and ANITA are currently searching for cascades
induced by ultra-high-energy neutrinos in ice. Moreover, several future
projects aim at both, high-energy cosmic-rays and neutrinos. SKA will search
for neutrino and cosmic-ray initiated cascades in the lunar regolith and
provide unprecedented detail for air-shower measurements. Finally, radio
detectors with huge exposure like GRAND, SWORD, or EVA are being considered to
study the highest energy cosmic rays and neutrinos.
