An implant is a way to semi-permanently boost skills of your choosing. Sounds pretty powerful right? Well, it is :)

I say semi-permanently because, while you don't have to do anything to keep the skills after you get the implants in, you can remove them pretty easily as well :) Note that you can also use implants solely to boost into other implants as well. But, i'm getting ahead of myself...

Ok, so, it's something that boosts skills, how do I get them and are they hard to put in?

There are a few ways to get implants. First, you can buy them in basic shops premade for your profession. You can also find them in missions (though these ones will most likely boost skills you have no interest in), or you can even build them yourself (or have other players build them for you).

Building them yourself requires putting IP into the "NanoProgramming" skill. I really wouldn't recommend this, especially not for someone starting an Advent and just investing low level IP.

Implants require Treatment (a skill under "Nano & Aiding") and some base ability (Agility, Strength, Stamina, etc.)

You can boost Treatment and abilities a number of ways. You can look here for some ideas on buffing treatment.