Argument from authority can be but is not always a logical fallacy. It is fallacious when, in the context of a deductive logical argument, the reasoning proceeds as:

1. Dr. So-and-So said p.
2. Therefore, p.

The fact that Dr. So-and-So said p does not provide a deductive logical reason for believing that p, and provides none of the evidence supporting p. (2) is not a logical consequence of (1).

An appeal to authority can also occur in an inductive context, where one is providing reasons and evidence in support of, but which do not necessitate, a conclusion:

(1) Dr. So-and-So's article in such-and-such journal concludes that p. (2) Therefore, probably p.

Such an appeal is fallacious when the authority lacks authority in the subject matter at issue--just because someone is an authority in one domain doesn't make them an authority in all domains. It is not fallacious when the authority is a genuine authority in the relevant area of expertise, but it is important to note that the evidence provided to the conclusion is non-conclusive and can be undermined or rebutted by further evidence.

While it's always better evidence to go beyond the authority to the arguments and evidence by which the authority came to their conclusion, as a practical matter this is not always reasonable, and it's impossible to do in all cases. Even within science, scientists appeal to published articles and even verbal reports of experimental or investigative results from other scientists as a basis for drawing conclusions--nobody has the time, expertise, or capabilities to perform all relevant experiments even within a discipline. This is a matter of the division of cognitive labor, and is neither fallacious nor irrational.

I got this answer from Skeptic Exchange and Skeptic Exchange is always right

would be a better example

i got this answer from wikipedia and wikipedia is always right

would be an example

'scientists say' is a great one. basically anything where a person says something like 'an expert on climate change thinks that global warming isn't man made' is a good example of it. the arguer is trying to take the statement out of the hands of the people debating the issue.

since neither person debating is an expert on climate change, the person putting forwards the argument will often state something like the following:

'Are you an expert on climate change? This guy has published papers and degrees in the subject so I don't see who either of us are to say we know better.'

it's a fallacy for a few reasons. one it presumes the incorrect belief that experts are infallible, which clearly they aren't. another is that it implies that all the experts are on the same page.

yes the experts on climate change that think it isn't man made do indeed know more than most of us about climate science, but then so do all the experts on climate change that think it is man made.