Vimal
EMC - electromagnetic compatibility
EMI - electromagnetic interference
These are terms used to (basically) describe if products give off levels of electrical 'noise' or can have their operation affected by picking up the same 'noise' from another source.
Electromagnetic_compatibility
Electromagnetic_interference
There are certain specifications for products and we'd have to know more about what the product is and what market you're selling in to, for example Europe.
The test are performed by either running the product (normally) in a 'Faraday' room (shielded from outside electrical influences) and an antenna is used to 'listen' to the electrical noise, or the product is bombarded with a variety of electrical noise while being operated, to see if it is affected.