Electrum has been around since 2011 and works with Windows, Mac, Linux and Android.
This means you can set it up in minutes and it takes up very little space on your hard drive.
Electrum uses a hierarchical deterministic wallet, which means a random ‘seed’ of 12 dictionary words is generated when you first launch the app, from which it derives the keys necessary to spend and receive BTC.
Electrum displays the seed as you create your wallet and requires you to write it down. This means that if you lose access to this version of Electrum, you can easily reinstall it on another machine and use the seed to restore your BTC.
Electrum offers you the option of encrypting your wallet file during setup, although you can choose to leave it unencrypted if you wish. You can also use Electrum in cold storage mode to create a ‘watching only’ wallet.
As a ‘thin’ client, Electrum relies on other servers for payment information, making it more vulnerable to certain types of hacking than full node wallets.