CoinJoin acts as an opaque wall in a timeline that transactions pass through. If a sender of bitcoin coinjoins, the recipient is unable to determine how the sender obtained the funds.
In bitcoin, the blockchain is the 1st dimension also known as layer 1. There are higher up and parallel 2nd dimensions that utilize the 1st dimension as its host. There may eventually even be layer 3 dimensions as more development continues.
Bitcoin can enable anonymous digital transactions, but it is good to understand where anonymity on Bitcoin can degrade. By understanding how anonymity can be eroded on bitcoin, one can then understand how anonymity can also be preserved.