Since 1980's the search method I knew goes like this based on Microsoft
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"CONTAINS is a predicate used in the WHERE clause of a Transact-SQL SELECT statement to perform SQL Server full-text search on full-text indexed columns containing character-based data types. CONTAINS can search for: A word or phrase. The prefix of a word or phrase. A word near another word". In other words it is a method to query database for specific words, phrases, or patterns within text data
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That means the part number or description in the title need not be exact, rather few letters in sequence match the search criteria to return result.
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According to eBay Manage active listings search, "contains" does not return an item desired unless the entire phrase submitted is exact. That makes search in Manage active listings difficult for editing. I usually resort to using browser "Find" method to find what I am looking for ...