The common-mode inductor, or common mode choke (CM choke), is a passive electronic component used to remove EMI. Common-mode chokes are designed for high-speed applications, for switch-mode power supplies and DC power lines, circuits with poor or no grounding, and circuits with signal and noise that are "mixed", or pretty much on top of each other. This device is designed specifically for its unique frequency-selective properties, and the windings are designed for EMI suppression effectiveness. Two windings are precisely wound on a common magnetic core, and the result is a device that can scrub out noise that is "very close" to your desired frequency, and return a clear and balanced signal.
An Inductor is a length of conductor, normally wire, wound into a coil (thus the nickname that some people call this device) and around a core to concentrate the magnetic force (field) and maximize the inductance. The more turns of wire in the coil, the higher the inductance value. Inductors can be found in all facets of electronic design so they are not specific to one application area. Its primary properties are to resist changes in AC (alternating current) and to store and release energy from its magnetic field.
Multilayer inductors can be made from one of two different cores, ceramic (air core) or ferrite. These inductors, when made in a ceramic core, usually possess high SRF’s and current ratings for higher frequency applications. When made in a ferrite core, the part will be naturally shielded and typically will have higher inductance values and higher Q factors at lower frequencies.
Thin film inductors are the tightest tolerance inductors made. These are made specifically for High Q and high current characteristics within high frequency and lower inductance applications. Normally this would include RF and wireless applications including but not limited to the following applications: Bluetooth, Telecom Market, GPS, PDA, cell phones, etc. Typically they are used for impedance matching on your RF circuit. Another use for thin film inductors is for creating a resonant circuit (tuning a circuit).
Wirewound inductors are the most versatile of the three technologies when it comes to their use in applications. This category of inductors includes not only chip inductors, but also all leaded inductors as well. A wirewound inductor will have the option to be magnetically shielded which helps it control unwanted signals from interfering with other components on the board. This is especially important in filtering applications.