When a honey bee colony outgrows its current space, the queen and roughly half the bees leave to find a new home. First they land on a tree branch, bush, or some other location usually 3-10 feet off the ground. This soft, fuzzy group of bees is called a swarm, and is typically the size of a football or basketball. They stay this way for a few hours or a few days, while scout bees are looking for a suitable place to live. Then the swarm leaves. (Honey bee swarms do not look like nests made of paper.)
If you see a honey bee swarm, like above, find a beekeeper!
These photos show wasp nests, which do not contain honey bees. Honey bees do not usually create nests in the open, preferring enclosed spaces.
While the swarm is formed, the honey bees are extremely gentle. They have no home to protect, no young to care for, and no honey stores. Call a beekeeper right away as soon as you notice a swarm appearing, so the bees can be collected and relocated to an apiary where they will be cared for.
Try to identify whether what you have are actually honey bees (bottom left) using the chart below.