When you learn vocabulary in a foreign language, some words will be more useful to you than others. Choosing the most important words out Learning a new language will help you quickly talk about your work interests or other important things. This means you have to be selective about learning new words. You have limited time to study every day. You can choose to learn useful words or useless words. Don't overthink it now.
When you encounter new words in the target language, ask yourself which words and phrases are Phone Number List most useful to me. You must follow this example at all times. Suppose you are learning French because You want to retire to a village in the south of France. You are still a relative beginner. You are studying a popular French textbook. In a specific chapter of the book you learn French words that you might need to get through airport security. Later that week you attend a language event and meet a friendly Frenchman who lets you practice your French with him.
As you get to know each other you will encounter words you don't know. Jot it down afterwards so you don't forget. The next day you have a moment to choose. Did you learn the textbook vocabulary about airport security or did you learn the words from conversations? The answer should be obvious. You may never need to speak French at airport security so the vocabulary will be of very low value.