The Talmud and its commentaries and related texts are famously difficult to understand. Adding to the difficulty are the multiplicity of versions: the oldest part of the Talmud, known as the Mishnah (from the early 3rd century CE) is mirrored by a parallel text, probably composed about a century later, called the Tosefta, which contains much identical material and a host of variations. Then there is the Jerusalem Talmud (or Yerushalmi), compiled around 400 CE and later largely supplanted by the 7th-century Babylonian Talmud. And each of these texts stems from manuscripts that themselves vary. Tamar Marvin provides an introduction to the subject:
There is something astounding about coming to know that the texts we take for granted, that we tend to see as stable and fixed, have a history of being handed down that is intimately connected to the lives of individual humans. We often don’t have much information to color our understanding of these individuals, but their handwriting serves as testimony to their presence and efforts. In most cases, the textual histories of even foundational texts hangs on a thread, resting on a small number of textual witness. (Textual witnesses are just what they sound like: manuscripts that serve as early evidence for the modern printed texts, or postmodern digital texts, that we see before us.)
There are, of course, plentiful manuscripts as a whole of such texts, but most are copies of each other (or of similar texts, no longer extant). In other words, there are few early exemplars that serve as “witnesses” to the version of the text coming out of antiquity, often, as for the Mishnah and Tosefta, out of orality and into textuality.