Samvatsara is a word in Sanskrit language that means year. It is similar to how we use the word "year" in English. However, in certain Indian cultures, particularly in Hinduism, the word "samvatsara" is used to refer to a cycle of seasons, which are based on the position of the sun and the moon. Every samvatsara is made up of twelve lunar months, and it starts on the day of the first new moon after the spring equinox.
To make it simpler, think of samvatsara as a special way of counting years that some people use. They follow a calendar that starts in the spring when the moon is new, and they don't start counting until that day. Then, they follow twelve lunar months until it's time to start counting again on the next new moon in the spring.
In ancient times, people used samvatsara to keep track of time for agriculture, festivals, and other important events. It is still used today by many people who follow traditional Indian calendars, especially for religious purposes.