Okay kiddo, so in Nepal, they have a special person called a monarch who is like a king or queen. When the current monarch (the person who is the king or queen at that time) passes away, they have to choose a new monarch to take their place. That's where a coronation comes in.
A coronation is a big fancy ceremony where the new monarch gets officially crowned or given a special hat or headpiece that shows they are now the new king or queen. During a coronation, there are lots of people who come to see it, like other important people from Nepal and from other countries.
The Nepalese coronation is a very special event because it has been happening for hundreds of years, even before you were born! During the coronation, they also have special music, dances, and rituals that make it a really big deal. It's like having a huge birthday party, but for a new king or queen!
So, in summary, the coronation of a Nepalese monarch is a big important ceremony where a new king or queen is crowned or given a special headpiece to show that they are now the ruler of Nepal. It's been happening for a long time and is a big deal for the country and the people.