> how is this possible when it's garbage collected?

Common Lisp lets you give "hints" to the garbage collector, so you end up with pretty much what you'd have in C but without the manual memory management.

> Is there a certain Lisp you would recommend that's practical enough I'd use it for projects?

Racket is very nice and comes with great documentation, a huge standard library and a very handy IDE. Clojure was hyped a lot so it has lots of libraries, which however might be of dubious quality or unmaintained by now, and it's on the JVM, which might or might not be a good thing for you. Common Lisp is very versatile and "pragmatic", but lacking in external libraries.