The Hebrew calendar is a lunar and solar calendar, meaning its months follow the moon's cycle around the world, whereas the secular calendar is only a solar calendar which follows the sun.

Christians started the years again when Jesus was born

but Muslims didn't

It is lunisolar. It is based on the solar year, with adjustments to keep the months in line with the lunar cycle.

The United States uses the Gregorian calendar, which is a solar calendar.

Lunar calendar