Given how broad the Interstellar ecosystem is, Interstellar might mean different things to different people.
2.1 A Secure Multi-token Wallet
You can use Interstellar as a secure digital wallet to securely store your fiat and crypto-currencies. As examples, Interstellar will help you securely store your Bitcoin, Stellar Lumens or any other Stellar based asset.
Another neat feature of Interstellar is its support for multiple accounts, which is essential when you want to have different accounts for separate transactions.
2.2 A Decentralized Exchange
Why focus on one currency when you can own them all?
Exchange crypto-currencies between peers without a middle man. Safe, secure with no risk of bankruptcy from the exchange.
Multisig(multiple signatures) will protect your account from thefts and loss.
Multisig is technology that forces your account to require multiple signatures before performing transactions. You could, for example, set up a 2 of 3 multisig account where 2 signers out of 3 are required to approve a payment before it is issued out.
Next, we'll discuss how to access the Interstellar app.