Final answer:
Part-of-speech tagging is the process of labeling words like 'John' as nouns. It is a step in information extraction relevant to natural language processing which helps in sentence structure understanding.
Step-by-step explanation:
In the field of information extraction, the process of labeling 'John' as a noun is known as Part-of-speech tagging (or POS tagging). This involves assigning parts of speech to each word in a sentence, such as nouns, verbs, adjectives, etc., based on its definition and its context within the sentence. Part-of-speech tagging is an important step in natural language processing tasks because it helps in understanding the grammar structure of the sentence, which is essential for further analysis such as parsing, named entity recognition, and so on.