There are two types of dock stations on the market:
Docks use external MagSafe adapter to charge MBP. (MagSafe should be bought additional from Apple).
Docks with only Thunderbolt connection to MBP.
With first one power supplying is clear. How does second type can charge MBP?
Is it possible to charge laptop through thunderbolt without MagSafe?
P.S. Consider MacBook Pro 2014-2015