Genymotion is a virtual device for run the Android apps. Using Android Studio you can make a virtual device with AVD Manager. But Genymotion is more powerful and useful software for Android development. It is very easy to config.
You can download Genymotion with following link.
To run the Genymotion, it need VirtualBox software. If you already install VirtualBox in your computer just download Genymotion only. But if you want to download both you can download both software using following link.
When you download it keep mind there are an option to choose what do yo want. (Only Genymotion or Genymotion+VirtualBox)
Download and install Genymotion. To use genymotion you have to log in to genymotion.
OK. to do it go to Genymotion web site and make a free account.
Then open the Genymotion & log in to it.
Add device to Genymotion
Then click on this Add New Virtual device button.
Then select android version you want and a device you want click download.
After your virtual device is downloaded click Start button.
Your virtual android device will start now.