If you click Search MSC the next screen appears with the Mathematics Subject Classification 2020.Each reference in MathSciNet can have 1 or more classifications. In addition, there is also a distinction between MSC Primary and MSC Secondary.
In the search bar you can fill in a classification like a keyword or a phrase or a 2-, 3-, or 5-digit classification.
Here you see an example of a search for a 2-digit classification 05 and their description. Under the Publications tab, you can select the MSC Primary or MSC Secondary field under Search Terms and search for the classification. After that, all results will appear with this classification.
When you click Show Historical Classes some classifications expand and more (red) classifications are visible.
If you click Download PDF you get the whole Mathematical Subject Classification Scheme from 2020 as a PDF.
MathSciNet’s Help function describes Collaboration Distance as follows:
‘An interest in the ‘distance’ between people has been popularized in both the mathematical community (Erdös numbers) and the general public (Six Degrees of Separation). In mathematical terms, this can be thought of in terms of the collaboration graph: the graph with authors of mathematical papers as vertices and edges connecting authors who have been co-authors on at least one paper. The MathSciNet database provides an example of a relatively large collaboration graph. The distance between two authors is defined to be the length of the minimal path (if a path exists) between the two authors in the collaboration graph. A search returns one of the minimal paths from the first author to the second author. It displays each edge in the path: each co-authored paper. For each edge it is possible to find all the papers authored by each author, as well as all the papers co-authored by the two authors’.
Enter the names of the authors for whom you wish to know the collaboration distance and click Search. Use Erdös 
is a reference to Paul Erdös (The Erdős number, named after the Hungarian mathematician Paul Erdős, is a way of describing the ‘collaboration distance’ in scientific articles between an author and Paul Erdős. Source: Wikipedia)
In the example below you can see that Klaas Landsman is linked to Stephen Hawking via Noah Linden. The Collaboration Distance is therefore 3.
In this screen you can select a period and see which Books, Journals or Proceedings recently have been added. Then click Search:
When you search for Books, this gives you the following result:
The Current Index to Statistics (CIS) is a bibliographic index of publications in statistics, probability, and related fields. It includes data from approximately 160 core journals, 1,200 additional journals in related fields, and 11,000 books. The bulk of the content in CIS is from 1975-2017.
CIS was developed by the Institute of Mathematical Statistics and the American Statistical Association.
When you search for algorithm and then click on Submit you get the next results:
In MR Lookup you can search for a specific article and get it in a format like MR Citation, BibteX, AMSRefs, TeX or EndNote.
MRef is a tool for creating standard references with links to MathSciNet. The reference (with the author names first) should be typed or copied and pasted into the box below. Often, only a portion of the reference is necessary for MRef to recognize the corresponding entry in MathSciNet.
You have a choice of formats like MathSciNet, Link, BibTeX, AMSRefs, Tex or EndNote.
