A tagset is a list of part-of-speech tags (POS tags for short), i.e. labels used to indicate the part of speech and sometimes also other grammatical categories (case, tense etc.) of each token in a text corpus.

English modified Penn Treebank part-of-speech tagset is available in English corpora annotated by the tool TreeTagger that was developed by Helmut Schmid in the TC project at the Institute for Computational Linguistics of the University of Stuttgart and containing modifications developed by Sketch Engine (currently pipeline version 2).

An Example of a tag in the CQL concordance search box: [tag="NNS"] finds all nouns in plural, e.g. people, years (note: please make sure that you use straight double quotation marks)

Tagset

Open class categories

POS Tag Description Example
JJ adjective green
JJR adjective, comparative greener
JJS adjective, superlative greenest
RB adverb however, usually, naturally, here, good
RBR adverb, comparative better
RBS adverb, superlative best
NN common noun table
NNS noun plural tables
NNP proper noun John
NNPS plural proper noun Vikings
VB verb base form take
VBD verb past took
VBG gerund taking
VBN past participle taken
VBP verb, present, non-3d take
VBZ verb present, 3d person takes
FW foreign word d’hoevre

Closed class categories

POS Tag Description Example
CD cardinal number 1, third
CC coordinating conjunction and
DT determiner the
EX existential there there is
IN preposition in, of, like
LS list marker 1)
MD modal could, will
PDT predeterminer both the boys
POS possessive ending friend‘s
PRP personal pronoun I, he, it
PRP$ possessive pronoun my, his
RP particle give up
TO to (both “to go” and “to him”) to go, to him
UH interjection uhhuhhuhh
WDT wh-determiner which
WP wh-pronoun who, what
WP$ possessive wh-pronoun whose
WRB wh-adverb where, when

Source: http://www.infonetware.com/tagset.html