The Midheaven, or MC, is the highest point of the ecliptic at the moment of birth. It marks the top of the chart and, in Placidus houses, the start of the tenth house. It is calculated from the exact birth time.
The MC describes reputation, direction and the contribution a person wants to be known for. That is not always the same as a job. Someone may earn a living one way while their real Midheaven work happens elsewhere.
The sixth house, by contrast, describes daily routines, tasks, colleagues and health habits. A satisfying working life usually needs both: a sixth house that functions and a tenth house that has meaning.
The MC's sign gives the style of the calling. Capricorn MC tends toward responsibility and long-term building; Pisces MC toward compassion, art or service; Gemini MC toward communication and variety.
Planets conjunct the MC are especially visible. Jupiter there may bring opportunity and recognition; Saturn, authority earned slowly; Neptune, a calling that is inspiring yet hard to define.
Transits and progressions to the MC often coincide with changes of role or public standing. Read them as invitations to align work with direction, not as promotions guaranteed by the sky.