I'm interested in the Metamask App (Android) and I'm wondering how exactly the sending of funds works: Since the 12 words (and the corresponding private key) are generated on my mobile device (correct?), what happens when I send funds to another address?
Is my private key sent (but hopefully not stored) to some server that handles the transaction? My understanding is, that my phone cannot do transactions on its own, since it doesn't have the whole ~300 GiB blockchain accessible?
This question is specific to Metamask and the Ethereum blockchain, but I guess the same question could be asked for Bitcoin (and some mobile wallet) or another blockchain.
Thank you for your help!