If you already have dentures, dental implants can be used to "lock" your denture to the bone. This is called an overdenture.
Please see this post for some overdenture basic information.
There are many choices for securing your implants to the denture. You should know that are bars or individual anchors. I will focus on the locator attachment.
This video will help you understand the basics: (if you cant see the video use this link http://www.youtube.com/watch?v=i8hb6_9Es6A )
Here is a picture of what they look like in the mouth:
This is a picture of the actual attachment that gets embedded into the denture.
Does this help you? Please comment below!