A seed node is a blockchain node that helps speed up witness replays, among other things like providing additional security via decentralization.
An RPC node is a development node that is necessary for developing applications that use the Steem blockchain. It requires much more RAM and storage capacity, as it's not just the blockchain, but also all the development libraries that applications use to operate.
Think of the seed node as just a copy of the blockchain, whereas the RPC node is the blockchain plus everything you need to make apps run off the blockchain.
A seed node is a blockchain node that helps speed up witness replays, among other things like providing additional security via decentralization.
An RPC node is a development node that is necessary for developing applications that use the Steem blockchain. It requires much more RAM and storage capacity, as it's not just the blockchain, but also all the development libraries that applications use to operate.
Think of the seed node as just a copy of the blockchain, whereas the RPC node is the blockchain plus everything you need to make apps run off the blockchain.