Do you mean scholars of religion or scholars within religious institutions (i.e, theologians)?

I'm going to answer this question with respect to Christianity, and walk you through the major sub-fields that Christian scholars train in.

New Testament: NT specialists generally train in Koine Greek, 1st century/2nd Temple Judaism, early Christian history, and Graeco-Roman culture and history. Their primary scholarly output focuses on interpretation of the documents in the NT corpus. Apart from Greek, they are generally expected to pick up at least one, if not several, ancient languages (Hebrew, Latin, Aramaic, and Syriac being typical candidates) and a reading knowledge in German and perhaps French or another modern European language.

Sub-field or cross-field specialisations for NT include Greek grammar and linguistics, textual criticism, and integrating other interdiciplinary theories into the NT field.

Old Testament: OT specialists generally train across the considerable field of the OT canon, and so Hebrew and Aramaic studies, possibly another Ancient Near East language (Ugaritic, for example), OT interpretation and history of interpretation, ANE history and culture, and archaeology. Archaeology is more often applied to OT studies than NT studies, but not exclusively (i.e. there are archaeological studies focused on NT-related topics).

Systematic Theology: Systematic or Dogmatic theology is generally the treatment of the beliefs or tenets of the religion organised into a logical system of some sort. When some people talk about 'theology' generally, this is what they mean. Another way to think about this is to think of Systematics as 'what must the world be like if the theology of the texts in the Bible is accurate'. It's kind of like a mix between Biblical interpretation and Philosophy.

Church History/Historical Theology: There's a bit of a difference between these two terms. The former is basically the History of the Church. Most Christian traditions teach this, at an undergraduate level, with a shema that begins with a broad overview of Early Church History, then a narrowing of treated periods/topics as they approach their own denominational distinctive. So for Roman Catholics that trajectory is much flatter. For Protestants, there tends to be a fairly rapid skimming over the Medieval period, and a heavy emphasis on Reformation studies. Orthodox seminaries tend to place much greater weight on the early Patristics.

Church History, when done well, is a properly historical discipline.

Historical theology is more theologically orientated and is interested in evaluating the emergence and development of doctrine in particular periods of history. It is still a historically orientated field, but it's more 'history of ideas' than 'history of religion'.

Specialists in this area tend to train in one area particularly, but often teach more broadly.

Ethics/Moral Philosophy: Specialists in this field tend to cross-train with philosophy and particularly ethical philosophy more broadly, in conversation with theology and theological ethics. Their work is mainly of interest (at a scholarly level) to those working in a theistic philosophical framework.

Certainly within a Protestant context, that covers the major fields that you see Christians get PhDs in and research in. Below I mention some other fields that are relevant.

Liturgical studies: Some traditions place a great deal of emphasis on liturgy and church practice, and this can be a field in itself. It often integrates a history of liturgical practice and development.

Religious Art History: This is well outside my experience, but I've heard excellent papers out of this area. Tracing the development and significance of, say, religious iconography.

Canon Law: More prevalent in a tradition like Roman Catholicism, a focus on the legal canons of the Church, kind of a cross-specialisation between Catholic Law and Catholic theology.

Studies of Religion: Particularly in secular colleges, you'll see religion treated as a separate field itself. This discipline is often an outgrowth of sociology and/or anthropology fields and applies those methods to a particular religion, or through comparative studies of religion.

I hope that gives some overview of 'religious' scholarship at least for one major religion.