Resigning (Inevitable Checkmate) I am a relative beginner to chess but have noticed particularly playing online a lot of players will resign if they lose a strong piece, for example, their queen.

Is this sportsman like? I wouldn't have thought so, but I read a thread on here that stated stronger players will resign if a checkmate is inevitable. I can only assume resigning has less of an impact on rating.
Yes, resigning a clearly lost game is indeed considered good behaviour. Sometimes not resigning is considered unsportsmanlike!

It makes no difference on the result of the game whether you resign, are checkmated, or lose on time - a loss is a loss. In any rating system I've ever heard of, the method of losing doesn't make a difference.

It's just that people don't like wasting time when they're 100 % sure that their opponent will win the game almost effortlessly with no danger of making a serious blunder.