Some Basics - different configurations

There are a variety of multicopter configurations out there, some of the most common ones are shown below

Quadcopter

Quadcopters are the most common configuration as they offer the best balance between lifting capacity, and cost

Tricopter

X8 Octa Quad

Hexacopter

Octa V

Y6 Tricopter

Why so many motors/props?
Some configurations have an more motors so they can carry heavier things such as fancy cameras.  The more motors also offer some degree of safety if something fails

Octacopter