If you grew up outside India and are only now learning why your parents check a specific time before starting something, here is the short version of the three concepts that come up most.
Rahu Kaal
One of eight equal daily segments (from sunrise to sunset), rotating by weekday, traditionally treated as unfavorable for starting something new. Routine tasks are unaffected; it mainly matters for beginnings like travel, a new purchase, or a ceremony.
Choghadiya
The day and night are each split into eight segments, and each is labeled good, bad or neutral, giving a faster way to pick a reasonable window for smaller tasks without needing the full tithi/nakshatra analysis a bigger event like a wedding gets.
Abhijit Muhurat
The single most stable and auspicious window of the day, roughly half an hour long, centered around solar noon. It is considered suitable for nearly any auspicious activity and is often used when no other timing information is available.
How they relate to each other
Rahu Kaal and Choghadiya divide the whole day into segments and rate all of them; Abhijit Muhurat is one specific, reliably good window within that day. Checking all three together, avoid Rahu Kaal, prefer a good Choghadiya segment, and Abhijit Muhurat is close to foolproof if you can use it, covers most everyday timing questions.
Check today’s timings
Use the muhurat page with your city selected to see all three for today at once.
This information is descriptive.