The fallacy of misplaced concreteness means that things are treated as real which are not real.

Reification is simply making something a fact that is not a fact.  For example, many concepts known as scientific facts are actually just theories we have come to accept.  People have these in their day to day lives.  You come to accept something as concrete when it actually is not.  This can lead to trauma and bad judgement.

Reification is, in essence, a process of dehumanization which is not entirely new in the annals of human kind. (enotes Christmas Not Just Once a Year)

A fallacy is a problem in judgment or reasoning.  The fallacy of misplaced concreteness is also known as reification.  An example is in the story “Christmas Not Just Once a Year” where a character reacts hysterically to the taking down of the family Christmas tree. 

As “Christmas Not Just Once a Year” depicts, the problem with misplaced concreteness is “depersonalization in modern society” (enotes Christmas Not Just Once a Year) when a family refuses to acknowledge the past or the mental illness that causes the character to react hysterically.