Hi and welcome to the forum
To burn a disc it is needed to send the correct sequence of instructions to the firmware. This can be done manually (i.e. you send all instructions by yourself to the firmware), or through a software purposely created to do this.
Of course, a proper burning software is the easiest way to do for most end-users. UBS drives, like a flash memory chip or an HDD, works in a different way, and actually a software is needed to read/write data on these devises too. The only difference is that this software is provided by default by the operative system (Windows explorer is a good example).
This is possible, but only with rewritable discs. Again, a dedicated software is needed (it is called packet writing software). This method, however, has a very high percentage of failure, because rewritable discs are not enough reliable and often the software are buggy. An USB pendrive is certainly much more reliable for this.
Other than using a packet writing software, the simple "Drag & Drop" operations are possible only for reading data from a CD/DVD and only when the disc content is not encrypted in some way. For example, it is not possible with commercial DVDs, because in these discs there is a protection that doesn't allow to copy the contents without an external software.
You can burn (i.e. write) whatever you like on a disc, even random binary data. Audio and video are simply the most diffuse contents that people write on their discs
Usually, the word "ripping" is used referring to extract (or to copy if you prefer) audio and video contents from a CD/DVD to another support (a hard disk for example).
As I said above, if the disc has not some sort of anti-copy mechanism, you can drag & drop every data. If you burned a CD with your pictures, you can copy all files from the CD/DVD to your hard disk, but without a proper ripping software you can't do this with a video DVD or a commercial audio CD.