You're investigating a protein and want to know what other proteins occur in the same pathway — or maybe what other experiments have been done with that pathway or protein, and what's been published. Being the Sherlock Holmes of biology that you are, you might also like to inquire about what alternative forms are known, or what other flavors of that protein exist across a particular population. "No problem," you might say, "I can answer all of those questions without batting an eye." Sure you can — if you like pain.