Electrum is a Bitcoin wallet with a focus on speed and simplicity, with low resource usage.

Electrum uses remote servers that handle the most complicated parts of the Bitcoin system, and it allows you to recover your wallet from a secret phrase.

Electrum features:

Safe
Your private keys are encrypted and never leave your computer.

Forgiving
Your funds can be recovered from a secret phrase.

Instant On
Electrum is fast because it uses servers that index the Bitcoin blockchain.

No Lock-In
You can export your private keys and use them with other Bitcoin clients.

No Downtimes
Electrum servers are decentralized and redundant. Your wallet is never down.

Proof Checking
Electrum Wallet verifies all the transactions in your history using SPV.

Cold Storage
Keep your private keys offline, and go online with a watching-only wallet.

Multisig
Split the permission to spend your coins between several wallets.

Add-ons
Electrum supports third-party plugins: Multisig services, Hardware wallets, etc.

Version History for Electrum:
https://github.com/spesmilo/electrum/blob/master/RELEASE-NOTES