Please folks, don’t expect newbies to know anything. That’s why were are considered newbies!
After 30+ posts, your newbie status is getting a bit long-in-the-tooth. There are newbies that have just started Arduino that come from other engineering fields and then there are newbies that are starting at the ground floor. It is very difficult to write for both groups which is why it is so very important that newbies of both categories read the forum stickies and try to provide details and code examples, etc.
That being said, many us older crowd started electronics early in our teens with Ham radio or electronic kits from Radio Shack (Or Lafayette or Allied/Knight Kit or Heath Kit, etc.) In these basic electronic projects one would build shortwave radios or even test equipment such as VOM and RF/Audio Oscillators. I’m looking at a VOM built in 1967 that still functions although it takes the tube circuit several minutes to stop drifting. Tubes… yes, those things that get hot and utilize high voltages! :o
Much of the old magazine articles from Ham radio, Popular Electronics, Radio Electronics are still available over the Internet. There are also some good forums on basic electronic circuits, one is http://www.hobbyprojects.com/ but there are many others. Such projects get you familiar with resistors, capacitors, diodes, transformers, soldering, etc.
However - we live in a time where the above, sans soldering, can essentially be done virtually:
I would strongly suggest you become familiar with the above and go through some of the excellent examples.
If you need to use a sensor and want to research a little about the electrical/physics associated with the device, a great place to do that is GSU HyperPhysics.
But probably the greatest asset you have is Google. I always recommend that if you are setting out to build a project that you attempt to find a similar project that covers around 50% of what you intend on doing in your project. For example, if you were wanting to use an RF12B radio, solar power, and wanted to check the mailbox status then you could craft a Google query: arduino solar mailbox monitor RF12B … never under estimate what a help Google can be if you just talk nicely to her.