Sometimes, voltages collide. When you have parts that expect/speak at different voltage levels, you have to build a mediator to smooth things out. This SparkFun BOB-10403 uses PCA9306 two-channel bidirectional voltage-level translator on a nice, small breakout board.
The DE-SWADJ is the adjustable version of the "SW0XX" step-down voltage regulators. Using the same form-factor as a standard 78LMXX style regulator, it is a much better way to give regulated voltage to your project.
This switching regulator lets you power circuits with higher and lower than the voltage of your power source!