It's obviously very much a beginner's question. While attempting to play this "TADA" sound effect, I noticed that on the website it's written just C. But when I press C twice it does not sound the same. How to achieve this?
Now that I checked the link with another browser and could actually see what exactly the notation was... I still think that it's a valid beginner question, but for slightly different reasons. ;) Here are the relevant bits from Chordify.net:
Yes, it has the letter "C", but it's not only the name of a single note, here it is a chord symbol, an abbreviation meaning the C major chord. In a chord, multiple different notes are played at the same time. To play a C major chord, you play the notes C, E and G. The chord symbol for a C minor chord is "Cm" and it has the notes C, Eb (E flat) and G.
When you see the letter C, you have to figure out from the context, whether it means the C note, or the C major chord, or e.g. a time signature. In a time signature "C" means "common time", 4/4.
This a valid question, and the notation is not self-evidently clear. If you know that "C" can mean a note, you may not know that it can also mean a chord, which is a different thing. Or if you know how to play "C" on the guitar or ukulele, you may not have realized that the thing you played was a chord, not a single note. I recently had to explain this to a beginner guitarist who had been playing "C" and other such things on the guitar, but had not been told about chords and notes. That information opened a new world for him. :)
In the following pictures, the letter C is used in two different meanings: chord symbol and note name.