Bucket Sorting is a generalization of a process of categorization (classification) of objects (or events) according to some set of pre-defined categories (buckets) which completely describes all the possible events or objects (each event belongs to at least one bucket).
It is an O(n) process, related to mapping (or a hashing). There could be a function from an object/event to a bucket/category.
Pattern-matching is a specialization (implementation) of a classification process. Matching against kinds or types of objects or events.