Automatic espresso machines automate a few aspects of the espresso coffee brewing. They can automate the brewed volume, or brewing time. This is obtained by using an in-line flowmeter attached to the grouphead, for volumetric control. Or they can have a timer for a timed extraction. Grinding and tamping are still manual.
Generally, an automatic espresso machine has almost all the brewing operations automated. The only two operations that are left for the barista are coffee grinding and tamping. Compared to a semiautomatic espresso machine that are more complex in operation, automatic machines control most of the operations automatically. The machine can control the length, (amount of water poured), the brewing time, brewing temperature and other parameters.
Compared to a super automatic espresso machine though, an automatic leaves more flexibility for the barista. Depending on the barista’s skills, this could be a good or a bad thing, because there is more error margin. A superautomatic will automate every step of the brewing process, which is a great thing for beginners. If the barista needs more control though, this will typically be more or less restricted.