Asterisms can include stars from one constellation. Or they can be made using stars from different constellations. One of the most famous asterisms is the Big Dipper or Plough. This asterism is made of stars from Ursa Major also known as the Great Bear.
The stars in asterisms appear together in the sky, but they are usually not close together in space. For example, there are 7 stars in the Big Dipper. The closest is 58 light years from Earth. However, the furthest is 124 light years from Earth. So these stars are very far apart. Also, it takes the light from the more distant star an extra 66 years to reach us here on Earth!