The biology Monte Carlo Method is a way to solve complex problems in biology. It works by doing something called "simulations". Simulations are like experiments that can be done on a computer, instead of in a lab.
In a simulation, you use a computer program to try out different possible solutions to problems. The computer will pick one of the solutions at random (like playing a game of chance, or rolling dice) and then see how it does. If the solution does well, the computer will keep it; if it doesn't do well, the computer will discard it and pick another solution. The computer will continue to do this over and over, picking and discarding solutions until it has found the best one.
This way of solving problems is called the Monte Carlo Method because it works kind of like a game of chance. Just like when playing a game of chance, the computer will eventually find the right solution after trying many different ones.