The CONTAINS function is a powerful tool for searching within text data stored in SQL Server. It's designed for full-text searching, meaning it can handle complex queries involving multiple words, phrases, and even stemming (finding variations of words). Unlike simple `LIKE` searches, CONTAINS can understand the context of the words you're searching for. This makes it more effective for finding relevant results in large text datasets. It's crucial to understand that CONTAINS is specific to SQL Server and won't work in other database systems like MySQL or PostgreSQL. Instead, those systems typically use `LIKE` or other full-text search mechanisms. The function works by indexing the text data, allowing for faster searches. This indexing process can take some time initially, but it significantly improves search performance over time. It's important to note that the CONTAINS function requires the full-text catalog to be enabled on the table you're searching. This is a crucial prerequisite for using the function effectively.