When you reserve a POAP with your email address, you are reserving the right to mint that POAP to an Ethereum wallet/address at a later date. This means that the POAP is not minted to (stored on) the blockchain. The POAP is still yours forever; however, it will not inherit the benefits of the blockchain (immutability, undeniability of ownership, etc.) until it is minted.
If you'd like to see how to now mint the POAP from an email reservation, see our guide: How Do I Mint a POAP I've Reserved With an Email Address?
Still confused about the difference between reserving and minting? Please refer to our article: What's the Difference Between Reserving/Minting/Migrating/Transferring a POAP?