In astrology, midheaven is one of the four important angles to be taken into consideration apart from the Ascendant, the Descendant and the Imum Coeli. It points to what area of career would suit you and whether you would be successful in your professional life. Midheaven just indicates the middle of the zodiac heaven. It is not a planet but it is an angle in the zodiac circle. It is also referred to as Medium Coeli or MC. It is the highest point in your natal chart.
The midheaven indicates the repute you earn in society and how you try to achieve it. It is a representation of how you are known professionally rather than personally which is indicated by your Ascendant sign. In other words it is the public side of you. The midheaven is the cusp of the 10th house in your birth chart. Knowing your Midheaven sign helps in understanding your career instincts in a better sense.