When it comes to understanding concepts like Ohm’s law, how current “flows”, understanding what a transistor is and how it works, or the basics of digital circuitry, it’s not always easy to visualize what is going on, especially if the focus of a course is more theory than practical.
Falstad.com has a great online circuit simulator. It runs in Java, but the program is for free download, so you can use it anywhere.
Waveforms can be plotted on a scope, all electrical values are displayed, the interface is simple and easy to use, and there are all kinds of parts you can make circuits out of.
Example circuits show how 555 internals work, different configurations of a transistor, logic gate basics, and …how should we say…more eclectic ones? (Valve circuit? Coolbeans.)
If you are the sort of person who learns by seeing something at work, this tool is for you. But regardless of what level of electronics a person is at, Falstad’s simulator is simple and powerful.