French kissing is an extension of "normal"
kissing, which consists of repeated
lip-mashing between two people. French kissing, or "
frenching" extends the basic lips-to-lips motions by bringing the tongue into play. This is for most people much more enjoyable than standard kissing, as the tongue, also a very sensitive organ, can perform a large number of actions, such as thrusting, licking, squirming, etc.
In this day and age it is normal for people to french kiss on first/blind dates and on other occasions, though there are enough people who resort to more simple methods of kissing before they brave the jump to french kissing.