Again, search the forum as there are many examples on how to use these, too many to list here.
Triggers are used for times events like a happy hour to change pricing
Actions are used to make SambaPOS do something like send an email, change price definitions, apply discounts, any many other features
Rules are used with Actions & Triggers to make SambaPOS do something at a particular time, like apply a discount when a customer is selected, display info on a Pole Display, respond to Ticket Tags being selected to gift products, or to activate a 2 for 1 deal when a product is selected
These features are the power behind SambaPOS (along with Ticket Tags) and allow many configurations to suit your requirements.