What is the difference between d’Alembert’s principle and Newton’s second law?

d’Alembert’s principle is an alternative formulation of Newton’s second law of motion that effectively reduces problems in dynamics to problems in statics.1

While Newton’s second law states that the force $F$ acting on a body is equal to the product of its mass $m$ and acceleration $a$ ($F=ma$), d’Alembert’s principle expresses this relationship as $F-ma=0$.1

In this form, the body is considered to be in equilibrium under the influence of the real force $F$ and a "fictitious" or inertial force equal to $-ma$. By introducing this inertial force, d’Alembert’s principle allows engineers and physicists to simplify the analysis of complex systems, such as machine components, by treating moving bodies as if they were stationary.12