This is a way of serializing the data or representing data in torrent, ex; we use JSON while dealing with APIs, and BSON while dealing with mongodb.

why torrent chose bencoding over json:

• json does not support binary format
• bloated
• mixed/varying key:value pairs

These above following drawbacks made the creators of torrent to chose bencoding over JSON in 2001, Bencoding is simple, deterministic, supports binary and extremely simple.

Bencoding supports ONLY 4 datatypes:

Bencoding is recursive in nature, which means we can nest list inside dictionary and vice versa infinitely. ex:

d
  4:name
  8:file.txt
  6:length
  i123e
  5:files
  l
    d3:foo3:bare
  e
e

// actual structure:
{
	"name"   : "file.txt",
	"length" : 123,
	"files"  : [{"foo" : "bar"}]
}