Differences:
1) Implicit wait is set for the entire duration of the webDriver object. Suppose , you want to wait for a certain duration, let's say 5 seconds before each element or a lot of elements on the webpage load. Now, you wouldn't want to write the same code again and again. Hence, implicit wait. However, if you want to wait for only one element, use explicit.
2) You not only need web element to show up but also to be clickable or to satisfy certain other property of web elements. Such kind of flexibility can be provided by explicit wait only. Specially helpful if dynamic data is being loaded on webpage. You can wait for that element to be developed (not just show up on DOM) using explicit wait.