We defer to all kinds of experts in our lives.  When we are not feeling well, we go to the doctor.  When our car starts to blow smoke and the engine is running rough, we go to a mechanic. Generally, we follow the advice of these experts in their fields because they know more than we do. That makes good sense. But what if we asked our mechanic about our health issues and our doctor about our car troubles? Would you trust them implicitly and take their advice? Perhaps we shouldn't. 

When discussing topics, an opponent may try to shut you down by quoting an expert on the topic. If that person is a known leader in that field, then perhaps they were right, but what if they quote someone you don't recognise, or maybe someone who is a leader in another unrelated field? Should you then just give up your argument?

When someone avoids answering your question by referring to the wisdom of an inappropriate or fraudulent authority, they are using the "faulty appeal to authority fallacy."