Short answer
Abhijit Muhurta is the 8th of the 15 daytime muhurtas, a roughly 48-minute window around local midday, traditionally treated as good for almost any important start when no better muhurta is available. The main exception is Wednesday, when many traditions avoid it. Check the exact time for your city, because local midday is rarely 12:00.
How ChiChakra reads this
ChiChakra divides daylight from sunrise to sunset into 15 equal muhurtas and marks the 8th. Its length changes with the season (about 48 minutes on a 12-hour day), and it centres on local solar midday, not clock noon.
How to use it
Good uses: signing a document, sending an application, a small puja, setting out on a journey or launching something when the day's other windows don't fit.
Skip it on Wednesdays. On Fridays and Wednesdays Rahu Kalam sits close to midday, so check the two don't overlap on your chosen day.
For big ceremonies such as weddings, your priest may still prefer a full muhurta.
Good to know
Abhijit is a general-purpose window. It doesn't override your Chandrashtama days or a family rule.