EMC testing vs. EMI testing

Electromagnetic Interference is a radiated or conducted signal that is unwanted that you are trying to avoid.

Electromagnetic Compatibility encompasses the standards and testing of equipment so that it can generally be expected to function properly in a shared environment. This involves testing devices to make sure that the EMI produced is under some limit, and testing to ensure that the susceptibility is above some threshold where most complying devices won't disturb it (or damage it, depending on the standard).

Additionally EMC susceptibility testing can check for immunity to environmental factors such as static discharge (ESD) and line transients that can occur in normal use.

EMC testing generally refers to both emissions and immunity testing. However some engineers refer to immunity testing as EMC testing and emissions testing as EMI testing.

Electromagnetic interference (EMI) generated by electronic products can be an issue both internally and externally to the product. Regulatory agencies such as the FCC put limits on the amount of electromagnetic radiation that a product can emit, either radiated (through the air) or conducted (through the power power supply). But also, even without the regulatory considerations, EMI can still be an issue for hardware manufacturers.

A product may negatively affect another product for instance through interference. The 4 electromagnetic coupling mechanisms are capacitive (e-field), inductive (B-field), radiated (EM field) or conducted.

Immunity testing (often called EMC testing) involves subjecting a product to several electromagnetic phenomena to verify that the product performs at a performance level (called performance criteria) set by a standard during and after the phenomena. Typical immunity tests include ESD, EFT, surge, conducted immunity and radiated immunity.

I wrote "The Beginner's Guide to EMC Testing" that you might find useful as well as this video which outlines the branches of knowledge required to solve the EMC problem.