Orbs have always been a question with paranormal investigators.  Most now, will not keep evidence of orbs.  In our beliefs, an orb is energy of an entity.  Orbs are going to look as a solid ball of light.  A lot of people and investigators get dust confused with orbs.  This is something that is normal and you will get better as you do more investigations.

Dust can look like an orb because it is circular and looks solid.  Most dust has a foggy look in the center, also it is not always a complete circle.  When you get a picture of an orb, make sure you zoom in and take a look.  The biggest problem I see with dust is that when people take photos and see hundreds of dust balls, they believe they are all orbs.  That is the biggest mistake.  Orbs don't move in clusters.  They normally move on there own.  If you go out ghost hunting let all dust in the area to settle before taking pictures.