Imagine the bidding sequence (opp's passing):
South North
2C 2S
3C 3H
3N 6C
6N pass
What can you tell about North and South's hands?
Here's what we learn one bid at a time.
2C - 22+ points or a hand that is within one trick of game (because of distribution).
2S - 8+ points, a good 5+ card spades suit headed by 2 of the top 3 honors. Also a hand that feels it is worth taking up bidding space to tell partner about his own suit before hearing her suit. (because he didn't bid 2D) Note, at this point the pair is in a game forcing auction, and has at least slam interest.
3C - opener's long suit. Presumably 5+ clubs. Says nothing about points.
3H - shows a two suited hand (spades and hearts), says nothing about points.
3N - This is a very descriptive hand. This game bid is not forcing. As such we know south has less than 3 spades (didn't support spades), less than 4 hearts (didn't support hearts), and doesn't have crazy distribution (didn't rebid a minor). Since she doesn't have crazy distribution, we know she has 22+ points. However, since we know she didn't make a forcing bid, she has at most about 24 points. (with more, she'd want to go to slam, knowing partner has 8+ points). So know we know south has 22-24 points, a balanced-ish hand probably with 5 spades.
6C - This is also descriptive. North is showing club support, so at least 3 clubs. So we know north has 5+ spades, 4+ hearts, and 3+ clubs. This only leaves one card we don't know about. We also know he has 11-12 points. With less, he wouldn't be comfortable going to slam, and with more he'd be looking to see if grand slam was available
6N - South has diamonds stopped (probably twice), and wants to play in the higher scoring contract.
As you can see, you can learn a lot from the bidding even without a lot of conventions. (only the first two bids were conventional, and only one wasn't natural.) The important thing to always remember is every bid is said in the context of what has already been said. And, unless forced, every bid should be either describing something new about the hand, or placing the hand in what is expected to be the final contract.