Part-of-speech tags are labels used in linguistics and natural language processing to categorize words based on their function in a sentence. Common tags include nouns, verbs, adjectives, and adverbs. These tags help in understanding the grammatical structure of sentences and the relationships between words. In computational linguistics, part-of-speech tagging is essential for tasks like text analysis and machine translation. By identifying the role of each word, algorithms can better interpret meaning and context. Tools like NLTK and spaCy are often used to automate this tagging process in various applications.