Online Bitcoin Wallet or “Hot Wallet” is a wallet that is available on a device and connected to the internet, like PC, Tablet and Mobile.
Since your wallet address in created online it can't be considered as 100% secure. while it is not considered secure enough to hold a “big” amount of money, it is still the easiest way to start holding Bitcoins. As long as your Bitcoin holdings are not too high, no one might attempt to steal. But you should be keeping all your recovery phrases and connect the wallet to at least 2 different devices.
If you want to learn more about other types of wallets like Cold Storage Wallets Click here, or here for Paper Wallets, or here for an extended article about Bitcoin Wallets.
so lets drill down to 3 different online Bitcoin wallets, each one is putting its focus on different aspects.
Exodus – The prettiest wallet of them all.
If you are just starting up with Bitcoin, Exodus will give you an easy way to learn how to handle your new Bitcoins.
It's supporting a few of the altcoins like Ethereum, Litecoin, Dash and more are being added. On the downside this online Bitcoin wallet works only with desktop, and doesn't support mobile. Exodus is considered less secure than other wallets since the software was developed by a company and it is not open source like other wallets.
Bitcoin Core – A full Bitcoin node wallet for hardcore Bitcoiners
While other normal wallets are SPV wallets or “Lite wallets”, this Bitcoin Core wallet is a Heavy cannon. On Lite wallets, other computers connected to the network validate the transactio. Put it in another way, your computer doesn't hold a full copy of the ledger, on Bitcoin Core, it does.
It is a strong wallet, for advanced users, but for most of us there is not use in downloading the complete ledger (which is more than 145GB). It takes a lot of time, but it is the REAL Bitcoin wallet. Bitcoin Core is available only on desktops, but it is still secure than most wallets because of the community driven development that lead to the creation of this wallet.
Blockchain – The Practical Wallet
Blockchain wallet is one of the most popular wallets out there. It is some kind of a hybrid wallet, while it does store your coins online the company dosent have any access to your private keys. You can connect to this wallet from both desktop and mobile app.
There are many other hot wallets out there. Some focus more on security like Armory or Copay, and some focus for other aspects like visibility or simply speed. If you are going for higher sums of money investment you should consider going with a cold storage wallet. In the meantime you can use any of those wallets. Nevertheless, remember to use all of their security options to keep your money as secure as it can be.