Sending of sexting pics has been made easier in the modern world to the ease of internet access and the rise of Smartphones.
Intense foreplay or petting may easily erode a set boundary and two parties may find themselves into the actual sex.
The word sexting combines two words- sex and texting.
Though common between teens, the practice has spread to adults also.
It's always best to talk with your significant other rather than spying on them, however.
If you're looking for information on catching students who are cheating online, see Wiki How's article, How to Detect Plagiarism.
When used appropriately, sexting sites can be healthy and very helpful in most relationships.