Dating courtship and engagement
It often involves romantic talk, holding hands, kissing, making out, and oftentimes sex. Courtship is the time-honored and successful practice of learning about someone enough to know whether or not the two is compatible for marriage.
There is a reason God wanted Eve for Adam, and he says it right in the beginning of our manual for life. By design men will at some point need help and support, and women will want to be a help meet.
This is fabulous in marriage and dangerous in casual relationships.
Prior to that time, marriage always involved much more input from the parents, and "trial relationships" leading up to marriage were not conducted at all.
Courtship, as discussed in more detail subsequently, seeks to emulate the Godly models described in the Bible that were conducted by God's people up until the invention of dating.
If we act like we're married before we've made that commitment, we're defrauding (and sinning).