I am the aforementioned Betty Bat who just got her implants this week (well, I got the first part, anyway).
I suspect that the links that Meryaten provided will give you an excellent description of implants, what they can do, the procedures, etc. Here's my addition as a "real life" case.
I had two baby teeth with no permanent teeth behind them. One was pulled when I was 12. As time went on (40 years of time!), my teeth started to shift around because of the space left after the departure of the baby tooth. I decided to get braces to correct the shifting, and my dentist recommended that I get an implant to fill in the space. At this point, I still had a baby tooth sitting there in my jaw - and I was 52 years old. The tooth wasn't in very good shape and both the tooth and the roots were much smaller than the other teeth, so I had the baby tooth pulled, along with a wisdom tooth, in preparation for my braces.
Unlike you, I had two spaces where the implants would go. I'm surprised that you would be advised to get implants if you don't have gaps for them to fill in. While I was in braces, I had a spring to widen the gap where the baby tooth had been out for 40 years - this was really one of the main benefits of my braces. My dentist said that he could have put in an implant in the smaller space, but it would be better if the space was widened. So, I had it widened. All in all, my braces experience went very well. I would expect that if you really don't have a gap where the implant would go or if the gap was small, then the ortho would use springs to widen the gap - and, IT DOESN'T HURT! I had no problem with my spring.
Before my braces went on, I had a consultation with an implant specialist to see if I would be a good candidate for implants. I would recommend this very highly. There are conditions under which implants are not suitable. Again, I think Meryaten's links will fill you in on this.
Initially, my implant specialist said that the implant surgery could be done 3 months before the braces came off. My ortho recommended waiting until after the braces came off, just to let everything settle in post-braces. I took my ortho's advice and had the implant surgery a month after my braces came off. I was told by my implant specialist that the surgery could be done before the braces came off, but he said that the wire would have to be removed pre-surgery, just for better access to your jaw.
Yes, it is surgery. I took a tranquilizer that the implant guy prescribed and then got local anesthetic in my jaw. I don't remember a thing after they swabbed my face and mouth with an antiseptic. Honestly, that's the last thing I remember. My husband drove me home and I took a long nap.
Knock wood, I haven't had any problems or any pain in the 4 days since the surgery. I'm taking an antibiotic and using Chlorhexidine mouthwash and rinsing with dilute peroxide.
The implants will heal for several months and then my dentist will install the teeth on them.
So, that's my story so far. I have a checkup with the implant guy in two weeks. Oh, and I guess the biggest problem is that I haven't been wearing my retainer since the implants went in because I need to go to my ortho to get it adjusted. You don't want to mess up the posts while they are healing.
Hope this helps. The biggest pain is in the pocketbook. Most insurance companies don't cover implants.