The tokens are locked on the blockchain, and those tokens are used as proof of your stake in the EOS blockchain.
As mentioned above, EOS Tokens will become fixed (non-transferable) on the Ethereum blockchain within 23 hours after the end of the final EOS Token distribution period which will occur on June 1, 2018 at 22:59:59 UTC. At this point the EOS Token distribution process will be complete and any person who wishes to launch an EOS Platform adopting the EOS.IO Software will be able to generate a JSON file mapping EOS public keys to the fixed balances of the EOS Tokens from the state of the Ethereum blockchain.
The EOS.IO Software is built such that any EOS Platform that adopts the EOS.IO Software will require approval of holders of not less than 15% of the total issued and outstanding EOS Tokens before tokens on such blockchain (the “Blockchain Tokens”) can be transferred. In other words, if the EOS.IO Software is adopted, it will be the responsibility of holders holding at least 15% of the issued and outstanding EOS Tokens to adopt one or more blockchains in order for Blockchain Tokens received on such blockchains to be transferrable.
As block.one will not configure and/or launch any EOS Platform, block.one will have no control over when, how or whether the EOS.IO Software is adopted or implemented, or how, when or whether the EOS Platform is launched. As such, you should not expect and there is no guarantee that you will receive any other cryptographic tokens or digital assets now or in the future.
In simple words?
The EOS tokens won't be used any longer and you will have a "share" of rights in the EOS platform based on those tokens that you had, prior to the lockup period that starts June 1 2018.
thanks fot the update