There are a number of things that make WhatsApp great for messaging, but one of the best things about it is the ability to use multiple lines. This means that you can have different conversations with different people on different lines, which can be really useful if you need to keep track of multiple conversations at once. It also means that you can easily switch between conversations without having to exit one and then enter another. This can save a lot of time and hassle, and it's one of the main reasons why WhatsApp is such a popular messaging app.