There are people who don’t say much, but know a lot of things and perhaps are even masters of what they do. And because they don’t boast on what they know they are called “unsociable” or “quiet” or “unfriendly”, etc.
But if someone constantly tells about what they know or have accomplished, they are called “boars” or “boisterous” or “egotistical”, etc.
So – what is your choice? Being quiet and just letting them wonder is my way (that way if you really don’t know what they are talking about, they won’t ask you any questions, relieving you of not knowing and feeling out of place and you can keep quiet, listen and learn).