Automated Watering systems consist of 2 basic components
1. Brains - Contoller
2. Guts - Pipes, control valve , anti-siphon (backflow preventer), filter, sprinklers, drip emitters
The controller (indoor or outdoor) is connected to the control valve via a low-voltage (24V AC usually) wire.

Source: Arizona Municipal Water Users Association (AMWUA)

Timer / Controller

Features 
    Water from anywhere (wi-Fi/Internet)
    Fixed Schedules
    Smart Schedules*
    Customizable Zone Parameters
    Offline Schedules
    Sunrise/Sunset Awareness
    Weather Skips*
    Cycle/Soak*
    Advanced Zone Details*
    Easy Installation
    
* Wyze requires Sprinkler Plus - 1 Year Included. $10/year

WaterSense labels two types of irrigation controllers that can help homeowners and businesses make their irrigation scheduling more water-efficient: weather-based irrigation controllers use local weather and landscape conditions to tailor watering schedules, and soil moisture-based irrigation controllers (also known as soil moisture sensors, or SMSs) monitor moisture levels in the soil to prevent irrigation when water is not needed.
According to the EPA, a WaterSense sprinkler controller can save the average U.S. home up to 15,000 gallons of water per year,

Most are mounted in your house or on the side of your house.
In-ground controllers are less common.

Most of the models we test allow you to operate them using the manual controls on the device itself and via an app on a smartphone. All work with digital assistants and/or smart home systems—such as Amazon Alexa, Apple Home (formerly HomeKit) and Siri, Google Home/Assistant, and Samsung SmartThings.

The connection to the valve is 24 volts.
The larger ones plug into a standard 120 v wall plug and an internal transformer that creates the 24 V output.
The smaller ones have an external 24 V transformer that plugs into the wall and supplies power to the connector.

Consumer Reports ratings

All have WIFI
RainMachine Touch HD-12 $260
Orbit B-Hyve 57950      $130
Rachio 8ZULW-C          $200
Rain Bird ST8-2.0       $290

Rachio 3           WiFi $200
Orbit 57950 B-hyve WiFi $133
Rain Bird SST600IN       $69
Orbit B-hyve       WiFi  $46
Orbit 57896              $53

Irritrol Rain Dial RD900-INT-R           $225
Rachio 3                                 $200
Orbit 57950 B-hyve                       $133
Hunter Sprinkler Irrigation XC600 X-Core  $88
Orbit 57985 B-hyve XR                    $146

Rain Bird 1-in Plastic Electric Inline Irrigation Valve $25

Orbit 57253 3-Valve Heavy Duty Preassembled Manifold $57

Orbit Anti-Siphon Valve 3/4 in. 80 psi $37