do I understand correctly that with your platform you can create your own blockchain?
Yes 
and what are the tokens on your platform for?
The tokens created and distribued while the ICO are used only for the fundraising.
Once the mainnet deployed and the tokens transfered on it, the tokens will be used as a gateway for crypto-currencies created on istrium.com and the other main crypto-currencies in the world (Bitcoin, Ethereum, etc.)...