As per Hinduism, there is a belief that astrology works on every creature, because planets and stars have their gravitational forces. So based on them in the Hindu calendar (which is moon-based), astrologers find and state the probability of a "suitable or good time" in a day for any work. It is believed that this time provides better results for work or that the person feels pure while doing work in this time.
This muhurat depends on the type of work and the situations of the planets and Nakshatras.
One can have multiple muhurts in a single day or one can have no muhurts at all for months
In short, "muhurat" is an auspicious time based on astrological mathematics.
Cho-ghadiya means four ghadi which totals to 96 minutes. Most of choghadiya are of a figure around 96 minutes.
Each day is divided into two time periods: Daytime - the period from sunrise to sunset Nighttime - the period from sunset to sunrise.
Each period contains eight Choghadiya's. The daytime difference is arrived at by calculating the difference between Sunrise and Sunset and dividing the same by 8.
These Chaudhadiyas are for performing prayers.