I’m pretty much copy-pasting myself here from past posts:
From David H. Lim’s The Dead Sea Scrolls (part of Oxford University Press’ Very Short Introductions series):
[INDENT]‘Text-type’ is an important concept that refers to the version of a particular document or literary composition. Let us say that you are composing a report or essay on your portable computer; you work on it for a while and save it on your hard disk in order to continue it at a later time. A good practice is to save the document in successive versions in order to minimize loss in the event of a crash or corruption of a particular file. Thus, you first save the file as ‘sampledocument.doc’ and having worked on it further save it as another file called ‘sampledocument2.doc’ and so on. If ‘sampledocument2.doc’ becomes corrupt, then you can return to ‘sampledocument.doc’, having lost only the incremental amount between the two. Moreover, you can revert to original formulations and calculations with this electronic paper trail. Each one of these files will share a common core, but will also be a slightly different version. If one were to ask which was ‘the original’ text, then the answer surely depends upon what we mean by the term. The initial commission of your thoughts to writing would be preserved in ‘sampledocument.doc’. However, if by ‘original’ you mean the copy that you sent off or submitted, then it would be the final or official version of the file.
In ancient times, ‘manuscripts’, as the word suggests, were written and copied out by hand. The production of literary works involved the compositional and copying stages, with the Qumran scrolls attesting to the latter. As we know from our own experience of copying, such a process is susceptible to expansions, contractions and all manner of scribal errors. For instance, our eyes could skip from one line to another or from one phrase to another that is either identical or similar. We could misspell a word or mis-form a letter. All these human errors contribute to the creation of different text-types. Other changes are intentional revisions of a text for ideological and religious reasons or mechanical ones, such as the stereotype or consistent rendering of one word by another in the target language.
Before the discovery of the scrolls, there were three previously known text-types of the Hebrew Bible: the Masoretic Text, the Samaritan Pentateuch and the Septuagint. The second of these refers to the Torah of the Samaritan community who consider themselves descendants of the ancient Northern Kingdom of Israel. The origins of the Samaritan community is a question of much debate; some sources hold that they were foreigners (2 Kgs 17.24-34), the indigenous people of Samaria (Ezra 4.4), or a sect that broke away from Judaism in the Hellenistic period (Josephus, Jewish Antiquities 11.340-345). The Samaritans regard the real sanctuary of God to be situated on Mount Gerizim and not in Jerusalem. They still reside today on that holy mountain in Israel and practise their own traditions. Their version of the Torah is characterized by expansionist and ideological readings. Strictly speaking the Samaritan Pentateuch refers only to the first five books, but the text-type is applied to the rest of the Hebrew Bible by analogy.
In the years following the discovery of the scrolls, Frank Cross proposed a local text theory that identified geographical areas with the three text-types. Accordingly, the Masoretic Text was representative of the Babylonian, the Samaritan of the Palestinian and the Septuagint of the Egyptian location. Cross classified all the Qumran biblical scrolls into one of the three text-types. For instance, 4QSam[sup]a[/sup] was considered a non-Masoretic Text much closer to the Vorlage of the Old Greek. Yet this text also has affinities with the Masoretic Text, the so-called proto-Lucianic text (a revision of the Greek translation), Chronicles and Josephus’s text of Samuel.
It became evident that the Qumran biblical texts could not be so pigeon-holed. A rival view was advanced by Emanuel Tov which posited a multiplicity of biblical text-types. Tov preferred to call them textual ‘groups’, but the more common designation is ‘text-types’. There were not just three text-types, but at least five or more groups of texts. Tov provided the following statistical data on the textual characteristics of the Qumran biblical scrolls: 35% were proto-Masoretic Text; 15% were pre-Samaritan; 5% were Septuagintal; 35% were non-aligned: 20% were texts written in the Qumran practice. Note that the total of 110% is due to the double counting of some of the texts in categories 1, 4 and 5, and category 4 is a ‘catch all’ for non-aligned and independent texts. Moreover, category 5 is a controversial group based upon the scribal practice of the Qumran community; not everyone agrees that this is a text-type.
It is now widely recognized that the Qumran biblical scrolls attest to a greater number of text-types than was previously thought. The Masoretic Text is surely an important text-type; it may even be argued that it was the dominant text-type, but there were several others that cannot be discounted. Some scholars, usually of the more conservative position, continue to hold the Masoretic Text as the text of the Hebrew Bible and all other text-types as translational, interpretative or recensional derivatives, even though they do not exhibit any of the relevant textual characteristics. This ‘Masoretic Text fundamentalism’, as it is called, prejudges the new evidence of the Qumran scrolls with unwarranted convictions.[/INDENT]