Country: India; City: Mumbai;
To better understand the Cryptocurrency Wallets you should take an example of a bank. Just like you choose Banks as third party service provider to keep your money safely and you keep some with you physically in your purse similarly you do it with Altcoins.
Cryptocurrency exchanges work as third party service providers, you trust, for trading, selling and buying. But, unlike banks you do not keep them there for long. As professional trader you constantly keep it moving to enjoying trading.