The third lecture is on the simplest Bayesian model, which is the Beta-Binomial model. Here the data is Binomial, while the prior is a beta density. For useful notes on this model, please see lecture notes given on the following link (please read these lecture notes to prepare for class).
https://www.cs.cmu.edu/~10701/lecture/technote2_betabinomial.pdfThe beta-binomial model (along with the closely-related beta-Bernoulli model) is probably the simplest interesting Bayesian model. It is tractable ..... calculations.
At the moment, the Wikipedia entry on the Beta-Binomial will be too difficult to read, but after having done the lecture or two on the concepts, you should be able to follow the discussion there as well: