LightWallet is a HD wallet that can store your private keys encrypted in the browser to allow you to run Ethereum dapps even if you're not running a local Ethereum node. It uses BIP32 and BIP39 to generate an HD tree of addresses from a randomly generated 12-word seed.
LightWallet is primarily intended to be a signing provider for the Hooked Web3 provider through the keystore module. This allows you to have full control over your private keys while still connecting to a remote node to relay signed transactions. Moreover, the txutils functions can be used to construct transactions when offline, for use in e.g. air-gapped coldwallet implementations.