I see in some math formulation that a certain angle is called, let's say
but there is a letter put in front of the angle notation.
What does the $m$ represent here? A factor?
$\angle ABC$ : The angle ABC
$m\angle ABC$: The measure of $\angle ABC$
So, when $\angle ABC \cong \angle DFG$ , that means, $m\angle ABC = m\angle DFG$
The notation $m\angle ABC$ typically denotes "the measure of angle $ABC$."
∠ABC refers to the physical angle itself while m∠ABC refers to its measure. There isn't any difference between these two and it is absolutely correct to use any of them...Some people just want to formalize things; these people think-"I have a car that is priced at 50000dollars, so i am driving a car and not 50000dollars" and so want to differentiate between little everything.