Electronics components range widely in size and function. From a beginner's point of view, it's hard to know where to start digging in. Programmer Christopher Pratt made a nice little beginner's guide over at Medium that runs through all the essentials to get you started.
Pratt's visual guide covers diodes, resistors, LEDs, transistors, relays, motors and servos. It's by no means a complete list, but it's well done and simple to read. It's certainly enough to get you started with DIY electronics projects. Head over to Medium for the full guide.