What can the Tesla app do?

Aside from scheduling service center appointments or otherwise communicating with Tesla Service, the Tesla app (for either iOS or Android) is one of the primary ways you can control your car. It should have already been set up as your Phone Key. You can control some aspects of charging (stopping, starting, charge level), you can turn on climate control and change its settings, you can lock, unlock, vent windows, open (and close if you have the appropriate hardware) frunk and trunk, turn on or off Sentry, Summon your car (depending on what features you purchased, that includes Smart Summon), you can request immediate Roadside Assistance, and you can of course spend more money by buying available upgrades.

There are lots of third party applications as well, which can provide handy analysis of battery usage, battery health, trip and charging statistics, and even provide some automation including voice commands to do all of the above. Note that third party applications do require you to authenticate with your Tesla account username and password and get a token, which some people are not comfortable with.

What voice commands are available?

For clarification, the Tesla app question was talking about voice commands enabled by third party applications on your smartphone. That depends greatly on the third party application and what you manually set up.

There is a fairly complete list of all available voice commands from inside the car here. There is also a list on the NotATesla website here. And, there is an iOS app available here.

How do I know if I have the latest software in my Tesla?

Tesla releases new firmware updates for its cars at least once a quarter (with major releases taking usually around a year to a year and a half to come out). There are times when bug fix releases seem to come every other week. Knowing whether or not you have the latest requires knowing what your car has (the smartphone app tells you, as does the center screen) and what the latest version is.

A handy way to determine the latter is with the TeslaFi Firmware Tracker. TeslaFi is one of those third party applications mentioned in this question, but you don’t have to be a paid TeslaFi member to see this data. There is a setting in your Tesla under the Software menu for Advanced or Standard updates. Advanced means you get new, generally available releases right away, while Standard puts you in a queue of unknown length before your car will notify you it’s ready. Note that downloading firmware updates requires being connected to WiFi, and the actual update usually takes 20-25 minutes; the car is not driveable while updating.