Quantum mechanics has a very definite formalism for computing probabilities of interactions. This means one can enter the boundary conditions to the solutions of quantum mechanical equations and get a predicted probability distribution. A specific measurement is one point in building up the probability distribution. In this answer of mine the probability distribution for the double slit experiment single electron at a time is displayed.
There are more than one mathematical formalism for calculating quantum mechanical probability distributions. "Interpretation" comes in in how one reads the mathematical formulae involved: the same mathematics, so it agrees with the usual solutions based on the postulates of quantum mechanics, but interpreted/read differently.
The many worlds interpretation, uses the path integral mathematics of quantum mechanical theory,
The path integral formulation of quantum mechanics is a description of quantum theory that generalizes the action principle of classical mechanics. It replaces the classical notion of a single, unique classical trajectory for a system with a sum, or functional integral, over an infinity of quantum-mechanically possible trajectories to compute a quantum amplitude.
The usual interpretation is to accept the path integral method as a very useful tool for organizing the calculations of probability distributions for specific interactions in a larger complete format.
The many worlds interpretations, takes this infinity of quantum mechanically possible trajectories as really existing, in an infinitely many worlds universe which exists for always. All possible paths have been already taken.
It is an interpretation that cannot be experimentally checked, because it interprets the same mathematics. It does not predict any differences in the outcomes to be checked by experiment.
How probable it is that it is a good interpretation is left to the mind of the reader, as there are nested infinities involved in every large or small quantum mechanical interaction. Keeping in mind that the classical emerges from the underlying quantum states, the mind boggles.