Are My Crypto Assets Stored In The Wallet Or The App?

Your digital assets are actually stored in a "wallet address" on the blockchain.
A Blockchain Wallet Address is a collection of corresponding public-private key pairs generated by the ECDSA (Elliptic Curve Digital Signature Algorithm). As the name implies, the "public key" is known to everyone and can be used to encrypt a message, while the holder of the "private key" can decrypt the message. In addition, the "private key itself" can also be used as a "digital signature" so that anyone holding the public key can verify whether the message really comes from the "private key holder (owner)".
Each cryptocurrency address consists of such a "public key-private key pair", and holding the "private key" for a particular address means having "ownership" of the wallet address.
Using CoolWallet is a way to protect your private key from being theft.
A "blockchain" is a growing database of transaction information. All transaction messages are confirmed by "Nodes" in the cryptocurrency network, and then the confirmed transaction messages are packaged into "blocks" that follow the previous block. When you execute a transaction, it will be broadcasted to the network. If the transaction is confirmed to have "sufficient balance" and "confirmed to be sent by the private key holder", it will be included in the next "block". Therefore, your cryptocurrency is not stored in the card nor in the application.