I always see good videos on Youtube. I mean that they are good in quality and in the presentation. So, what are the tools or programs which helps in that?
What you need is no different from what you need for any video production effort. You need a decent camera and camera work, which likely involves a decent tripod, decent lighting, decent scripting, decent acting, decent editing and decent compression.
The camera and camera work ensure that the video is clear and that it isn't distractingly shaky and that angles and shot composition look good. Decent lighting ensures that the camera can get good color and that there aren't weird or distracting shadows and helps things look pleasing to the eye.
A very wide variety of cameras could do the job, starting with cameras like entry level DSLR video or cameras like the GoPro. Lighting can be done with any set of similar type lights, though specifically made studio lights will output the whitest light which is helpful for filming, but isn't a necessary expense for starting out. It is important to make sure the color of the lights match though or you will get weird looking issues.
Decent scripting and acting ensure that there is interesting content that is well performed. Decent editing ensures that the source material is pieced together in a way that flows nicely and tells the story that is visually interesting and properly paced.
Editing generally is done with a piece of software known as a non-linear editor or NLE for short. Adobe Premiere Pro is a popular NLE, though in a pinch, cheaper alternatives can be used to produce satisfactory results, though they are generally more difficult to work with.
Finally, decent compression of the final video ensures that it looks good on Youtube, even at the limited file sizes that Youtube displays. This simply involves the use of a video compression software. Many good NLEs include a video transcoding and compression package (such as Adobe Media Encoder) and there are also free ones available, such as FFMPEG. VBR 2 pass, H.264 is the general compression of choice for Youtube, but some fine tuning of the bitrate, resolution and keyframe interval can make a big difference on the overall quality of the video.
Overall, to pull off a top notch video requires a fair bit of preparation, gear, knowledge and experience and it isn't going to be possible to detail everything you need to know in a single question and answer, but hopefully this gives you an idea of the key components involved in the process of making such a video.