Mechanics of a trigger

Hello. I'm struggling to understand the inner workings of a firearm. I'm not new to guns but still learning about how they're made of and function. I'm watching videos and reading articles. I've heard terms like single action vs double action, trigger pull, pre cocked hammer, etc. Someone with better knowledge than myself please explain the mechanics of triggers. Or even better convince me to look elsewhere to learn.<br><br>Edit: I'll mention that I have a Smith and Wesson 40sf. I've heard that it's single action but not sure, i know it's striker fire. I do know that the hammer is only cocked partially when a round is chambered, i think you only need to cock the hammer about half an inch for the weapon to discharge. I'm not sure how it works. Thanks for the comments guys.