ESP8266 and ESP32 required some special arrangement to pull the chip into boot mode. Typically this is done by pulling GPIO0 to GND. Now typical USB programmers doesn't provide this feature. so you have to manually do it. keeping that in mind this USB to TTL converter is specifically designed to program ESP chips. It has 6 pins

1. VCC
2. GND
3. TX
4. RX
5. RESET
6. GPIO0

The RESET and GPIO0 are connected with a duel transistor configuration that allows this programmer to put the ESP chip automatically into boot mode and reset automatically after the program successfully uploaded.

The circuit is based around CH340C USB bus convert chip and the logic level of the TX and RX pin is 3.3v which is suitable for ESP chips but using it any 5V microcontroller can also be programmed