Dating - a couple who have no relationship with each other, who go on continuous dates to see if there is a connection and can lead to some sort of future together,
a couple that have a relationship with each other, who go on continuous dates and outings to be together.
Tied - wedded, married, hitched, vowed to one another to spend the rest of their lives together.
This is how I see these words.... It was fun to be single, wild and free, have no strings attached to someone because it bears no consequence, experiment, and just have fun.
After dating people, going out to eat, spending time together, getting to know each other, and finding the right person it can eventually lead to tying the knot!
Married, exchanging vows of commitment to one another for life.