As seen from the Earth, a solar eclipse is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks ("occults") the Sun. This can happen only at new moon, when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy. In a total eclipse, the disk of the Sun is fully obscured by the Moon. - Wikipedia
This is the first day of summer in the northern hemisphere, and the first day of winter in the southern hemisphere. The Sun will have reached its northernmost position in the sky, with the north pole tilting towards the sun.