What I hear:

"But, evolution is just a theory, not a fact."

What they don't understand:

Merriam-Webster defines theory(2) as: abstract thought: speculation. However, evolution is a scientific theory, not a theory. Theory(5) is defined as: a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena.

See Wikipedia for a definition of Scientific Theory: A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.

What it means:

The educational system in the United States is failing. The basic meaning of the scientific process is not being explained.

Stephen J. Gould complained that basic science textbooks of the 1930's contained full chapters on evolutionary theory. Today's science textbooks contain at most a paragraph or two.

In addition:

A Scientific Theory, to be valid, must be both testable and falsifiable.

In other words, it must make predictions about future observations, and it must support negative tests designed to invalidate it. Evolutionary theory has been passing both criteria for 150 years.

If a theory cannot be tested and cannot support falsification, it is not a scientific theory, but a belief.