A period of one day and one night, a date: in the West, this is a period of 24 consecutive hours.
One day of sidereal time; the time in which Earth rotates once around its axis, relative to the point of the vernal equinox (about 23 hours, 56 minutes, 4 seconds).
The rotational period of Earth; the time in which Earth rotates around its axis 360 degrees.