Orion is visible on winter evenings but not summer evenings because of

A cluster of stars which resembles to any particular shape are called constellations.

In our sky, there are almost 88 constellations which are known to us.

Orion is the one in 88 constellations,

It is visible in winter season.

We cannot see all the constellations in all the seasons.

Because it is winter constellation and lies in the day sky during summer

Explanation:

The celestial sphere or the sky above us has been divided in to 88 different areas just like we have countries on Earth. These areas are known as the constellations. In each area when you join the brightest stars you can imagine a pattern. Orion is also one of these 88 constellations and favorite of many astronomers.

All the constellations are not visible through out the year. The reason is revolution of Earth around the Sun. The constellation which lie behind the Sun will appear in the sky in the day time and thus will be invisible to us. While those which appear in the night sky can be seen. Thus, constellations are also seasonal. Some can be seen in winter and some in summer.

Orion is a winter constellation because it appears in the night sky during winter. During summer it appears in the day sky thus can not be seen.