について is a particle-like expression that marks the subject of discussion, thought, or writing. It is used when you want to specify what you are talking about. For example, 日本について話す means 'to talk about Japan'. The noun before について is the topic, and the verb or sentence after it says what you do regarding that topic.

It often appears with verbs like 話す (talk), 考える (think), 書く (write), 聞く (ask/listen), and 調べる (investigate). You can also use it with the verb です to say something like 'about...' in a statement, though についての is used before nouns (e.g., についての本, a book about...).

In everyday conversation, について is common and neutral, but it is slightly more formal than just using the topic particle は. It is also used in writing and official contexts. When you want to ask for someone's opinion, you might say についてどう思いますか. Note that について does not mark the subject of the action itself; it only marks the topic under discussion.