Check out a getting started with Arduino book or online tutorial series. You're going to get a ton of answers from people that point you at all kinds of differ

Check out a getting started with Arduino book or online tutorial series. You're going to get a ton of answers from people that point you at all kinds of different boards and hardware to learn from, but IMHO nothing is as well documented and easily available as classic Arduino hardware (like the Arduino Uno) and its ecosystem of libraries and programs/sketches. Everything you learn from Arduino will help you the further you get into embedded programming and hardware fun.