The ESP is just a microcontroler running @3.3V as well.
When you're new, don't start with a separate ESP (ESP-01 to ESP-14) module.
Get yourself a proper development board: NodeMCU - WeMos D1 - Witty Board - ESP Thumbdrive
ESP power requirements are 3.3V±10%@500mA
The ESP8266 IS NOT 5V tolerant on ANY pin (see item 5.14 on page 25 of the FAQ)