The Tolkappiyam refers to a book on Tamil grammar. Option 1 is incorrect as it mentions a step-well of Western India, which is unrelated to the Tolkappiyam. Option 3 is incorrect as it mentions a collection of Tamil bhakti poems, which is a different literary work altogether. Option 4 is incorrect as it mentions a collection of Kannada poems, which is a different language and not related to the Tolkappiyam.

The Tolkappiyam is an ancient Tamil text that is considered one of the oldest surviving works on Tamil grammar. It is a foundational text for understanding the rules and structure of the Tamil language. The Tolkappiyam covers various aspects of grammar, including phonology, morphology, syntax, and semantics. It provides detailed explanations of different types and forms of Tamil words, sentence construction, and the classification of words into different categories. Additionally, it also discusses the use of language in poetry and literature. The Tolkappiyam is an important source for scholars studying Tamil language, literature, and linguistics.