  This article reviews current efforts and plans for gravitational-wave
detection, the gravitational-wave sources that might be detected, and the
information that the detectors might extract from the observed waves. Special
attention is paid to (i) the LIGO/VIRGO network of earth-based, kilometer-scale
laser interferometers, which is now under construction and will operate in the
high-frequency band ($1$ to $10^4$ Hz), and (ii) a proposed
5-million-kilometer-long Laser Interferometer Space Antenna (LISA), which would
fly in heliocentric orbit and operate in the low-frequency band ($10^{-4}$ to
$1$ Hz). LISA would extend the LIGO/VIRGO studies of stellar-mass ($M\sim2$ to
$300 M_\odot$) black holes into the domain of the massive black holes
($M\sim1000$ to $10^8M_\odot$) that inhabit galactic nuclei and quasars.
