If you like a video that someone has posted on YouTube, it is a good idea to leave a response to the video. To leave a comment, you must log in to your account, and under the video there will be a comment box.
you can always ask the owner of the video that has the response
You go to the video which you want to send your response and under the top comment you'll see it
Go on to the person's video you want to leave a response to, click on where you would usually comment but don't comment! There is a small icon to the right of the comment box that looks like an old video camera and click it. YouTube then gives you the option to either record video from webcam, upload a video response directly to the video, or choose a video you have already uploaded (keep in mind that you can only post a video as a video response once).
You can either upload your video as a response to the one in question or provide a link to it in your video's description.
If you want to create a responce video you can (create it first with your camera and editing software and save it... or) upload a live webcam response. Go to add a comment response to the video as you normally would, and to the right of the text box click on the link that says "Create a video response"
You first make a video, post it on Youtube, then go to the video you want to respond to. Look under the video and press "Send a Video Response." After you do this it will take you to all of your videos, click the one you want and your done.
Video Response is like u reply to the video you watched by making a video and put it on a title Re: (something something) that means ur replying to the video ur wathing (responsing what u wanna say)
You can post to Youtube on your own account, but the reply function currently doesn't do video replys.
Responses to different videos. Let's say you have a contest and to link it to that contest you just have a "Video Response" so you know that person can get it. It's a helpful tool.
There are varieties of YouTube videos like this @Kinhaspace
Youtube is great for this. Just upload the video as normal, and then when it is viewd a "post a video response" button will appear. The viewer can then click on that and upload one. This video will then be displayed beneath the one it is responding too.
You would have to download the YouTube video. Unless the video is under a Creative Commons license, downloading a YouTube video is against the YouTube Terms of Service.