This is a very good visual introduction to Machine Learning created by the team at R2D3 and helps even non-tech people understand how ML works and that training a model is balancing bias and variance error rates. Part 1[0] goes over what decision trees are, and Part 2[1] goes over Bias-Variance Tradeoff.
[0] https://r2d3.us/visual-intro-to-machine-learning-part-1/
[1] https://r2d3.us/visual-intro-to-machine-learning-part-2/