What is sidereal time?!
Question: Sidereal time is a measure of the position of the Earth in its rotation around its axis, or time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical to, the motion of stars. They differ by the precession of the vernal equinox in right ascension relative to the stars. Earth's sidereal day also differs from its rotation period relative to the background stars by the amount of precession in right ascension during one day (8.4 ms).[1] Its J2000 mean value is 23h56m4.090530833s
Answers: Sidereal time is a measure of the position of the Earth in its rotation around its axis, or time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical to, the motion of stars. They differ by the precession of the vernal equinox in right ascension relative to the stars. Earth's sidereal day also differs from its rotation period relative to the background stars by the amount of precession in right ascension during one day (8.4 ms).[1] Its J2000 mean value is 23h56m4.090530833s
Short version:
Sidereal time is measured by the rotation of the Earth, with respect to the stars (rather than relative to the Sun). One sidereal day is the time taken for the Earth to rotate once with respect to the stars and lasts approximately 23 h 56 min.
More specific:
Sidereal time is the hour angle of the vernal equinox, the ascending node of the ecliptic on the celestial equator. The daily motion of this point provides a measure of the rotation of the Earth with respect to the stars, rather than the Sun.
"Local mean sidereal time" is calculated from the current Greenwich Mean Sideral Time plus an input offset in longitude. Applying the equation of equinoxes, or nutation of the mean pole of the Earth from mean to true position, gives you local apparent sidereal time.
Another way to get "local sidereal time" is the right ascension (RA, an equatorial coordinate) of a star on the observers meridian.
Astronomers use local sidereal time because it corresponds to the coordinate right ascension of a celestial body that is presently on the local meridian.
I hope this isn't too technical and helped you.