dToken can be understood as the equity token for any vault, which represents your share of equity in the vault. Using EOS as an example, you can get slightly less than 1000 dEOS by depositing 1000 EOS. If the current price is 1 dEOS = 1.01 EOS, then you can mint 1000/1.01 = 990 dEOS. If there are 99,000 dEOS in the entire vault, it means you own 1% of the total EOS in the pool.