Welcome to the site. I encourage you to hit the
'search button' and type in key words to find out information about CAI and many other questions that you may have. Alot of new users to this site immediately post and don't realise that alot of simple and complex questions have had threads sometimes multiple threads already posted with all the answers to their questions.
Also, if you are very new to the car scene or you don't know the basics eg CAI, then I suggest going to a search engine like google and type in your required information. We all were very green on cars and not technical at one time in our lives, but instead of someone explaining the basics, there are many pages of info out there that will help you get started.
For the record, CAI stands for Cold Air Induction. This refers to the vehicle getting cooler air to feed the engine instead of sucking hot air from within the engine bay or from within the factory restrictive airbox. Cold air has the benefit of making the car more efficient and increasing power sometimes only marginally in different circumstances. The colder air is more dense than hot air and this is what an engine loves to breath. Depending on the vehicle, gains from doing this modification vary. There are definetely no negatives to giving the car cooler air to breath
Welcome again.