What are "anchor regions" in the human genome?
Good question. Anchor regions are regions that connect to the nuclear matrix. More specifically, in eukaryotic organisms, chromatin is anchored to the nuclear matrix by short DNA sequences of about 100-2,000 bp called matrix attachment regions or MAR. To answer the second part of your question, there are many categories (and opinions about those categories) of anchor regions. The most comprehensive way of categorizing these regions however I believe is by whether they are constitutively (always) or transiently (sometimes) bound to the nuclear structure.