Real-time versus scheduled
As you will likely consider as you read on, this could also be phrased similar to a section in Chapter 2, SFMC Automation Tools, as Comparing Journey Builder and Automation Studio. But even that is not fully accurate as there are ways to do both strategies in each tool. For instance, there are ways to do scheduled email sends inside Journey Builder through different Wait Activities and Entry Events and you can use File Drop automations in Automation Studio or even Triggered Sends and Transactional Sends (from Email Studio) to perform real-time messaging.
Although both strategies are available in both tools, each tool is explicitly designed to specialize in one or the other. Journey Builder can most definitely do scheduled sends through different entry event or wait options, but it is specifically designed to be a real-time marketing strategy tool. Similar to that, Automation Studio has options for real-time delivery/action, but it is most definitely optimized...