Regex phrase matches a specific sequence of regex queries. Think of it like a conjunction of regex queries, with positions and ordering of tokens enforced. For example, the regex phrase query for ru.* shoes will match running shoes, but will not match shoes running. 
SELECT description, rating, category
FROM mock_items
WHERE description @@@ pdb.regex_phrase(ARRAY['ru.*', 'shoes']);
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phrases
required
An ARRAY of expressions that form the search phrase. These expressions must appear in the specified order within the document for a match to occur, although some flexibility is allowed based on the slop parameter. Please see regex for allowed regex constructs.
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slop
default:0
A slop of 0 requires the terms to appear exactly as they are in the phrase and adjacent to each other. Higher slop values allow for transpositions and distance between terms.
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max_expansions
default:16384
Limits total number of terms that the regex phrase query can expand to. If this number is exceeded, an error will be returned.