There is not a lot to AutoPlay, but disabling it can help to prevent potentially unwanted programs (PUPS) from silently installing on your personal computer. AutoPlay is Windows built in mechanism to control applications and devices for your convenience, as with anything digital people with bad intent use it too.
Disabling AutoPlay stops your computer from auto running various devices like USB hard drives, flash drives, DVD/CD-ROM drives. This will stop your movie software from automatically accessing and playing a movie in the DVD-ROM drive. For some the benefit does not outweigh the risk (in this case a bit of inconvenience) of learning how to run applications and or disks manually. If you do try turning off AutoPlay and you don't like it you can always return and enable it.
AutoPlay has a number of benefits, so before turning AutoPlay off be sure you don't already use them. Some settings are beneficial and can make using a personal computer that much easier. For example being able to connect a device and have the pictures or files download automatically with no interaction is great. If using AutoPlay take a moment and look under the default actions and see if there is not an option that could aid you in your day to day computer work flow. Depending on your personal computers configuration there will be more or less options than pictured.
If you followed steps 1 - 3 AutoPlay is Off.
AutoPlay accessed via the Control Panel offers a different view. As Windows 10 matures things may change, but at this time there are two separate locations for AutoPlay settings.
To open the control panel right click on the start menu and select Control Panel.
If you open the Control Panel and do not see AutoPlay as an option locate View by: Category and change it to icons. See below.
If the wrong application opens when called form another application this is where it is set. Link to Choose default apps at bottom of AutoPlay settings. See above image 3. AutoPlay.