CiteScore is Scopus' journal metric, related to but not identical to Web of Science's impact factor. A journal's CiteScore is based on the number of articles cited in the journal, from the most recent three years of the journal's contents.
"Calculating CiteScore is simple and is based on the average citations received per document. CiteScore is the number of citations received by a journal in one year to documents published in the three previous years, divided by the number of documents indexed in Scopus published in those same three years."
SJR (also known as SCImago journal rank) is another metric that Scopus uses to modify their journal rankings. It is commonly seen on journals' own websites.
"SJR is weighted by the prestige of a journal. Subject field, quality, and reputation of the journal have a direct effect on the value of a citation. SJR assigns relative scores to all of the sources in a citation network. Its methodology is inspired by the Google PageRank algorithm, in that not all citations are equal. A source transfers its own 'prestige', or status, to another source through the act of citing it. A citation from a source with a relatively high SJR is worth more than a citation from a source with a lower SJR."
"SNIP measures a source’s contextual citation impact by weighting citations based on the total number of citations in a subject field. It helps you make a direct comparison of sources in different subject fields.
SNIP takes into account characteristics of the source's subject field, which is the set of documents citing that source. SNIP especially considers:
SNIP is the ratio of a source's average citation count per paper and the citation potential of its subject field."