I have been using this converter call it converter A to communicate an MCU through its UART pins RX TX. And I wouldn't call this RS232 because RS232 is about physical layer and voltage levels as explained below:
But now there's a driver which for communication requires this RS232 TTL module call it converter B. Is this still the same type I have or different? I mean is the converter A and B same type? If so, why confusing naming them as RS232?
No, it is not OK to call an UART as RS-232, because they are two completely different things, located at different layer on OSI model for networking. RS-232 would be the physical layer, and UART would be the data link layer.
Which means, UART can be used with other physical layers too, such as RS-485, RS-422, etc.
Some people mix RS-232 physical layer with UART, because technically all RS-232 ports were implemented with UARTs, and when you just want the UART many chips are still called 232 like FT232 because it is a USB UART which can be used to implement an RS-232 port.
Both those modules are just 3.3V TTL/CMOS level UART modules. They have nothing to do with RS-232. Or rather, they can be thought as typical computer RS-232 serial ports but with the RS-232 part left off, which is what might explain why they are called incorrectly.
RS-232 is a standard for physical electrical interface. It defines things like voltage levels and connector.
What it does not define is the logical bit serial protocol, line code, or encoding.
Those are defined by the UART. The UART uses logic level voltages, and these logic level voltages are converted to RS-232 voltage levels with a level conversion PHY when making an RS-232 interface. But in your case, you do not need RS-232 and need only the logic level UART signaling.
You are correct, those 0/5 V levels are not 'RS232' physical layer, which uses up to +/- 15 V. Many people say RS232, when they mean UART, the protocol, regardless of which physical layer is used to transport it. RS232 is perhaps the best known and oldest of the serial links, so it has become the Thermos, Hoover or BandAid word to describe them.
The CH340 you link to, and just about every other cheap 'TTL RS232' converter, outputs and accepts the TTL-like levels you have illustrated. However, there is one caveat, the levels are often 0 and 3.3 V, rather than 0 and 5 V. TTL is really a 0/3.3 V signal, it doesn't guarantee a 5 V output, and rarely gets near it, except with an external pullup.
Some modules are switchable 3.3/5 V output. I don't know whether 3.3 V modules will accept 5 V signals without damage. With luck they'll specify whether they do or not. I would hope that 5 V modules would accept 3.3 V highs as inputs, it's on the edge of a CMOS high specification, though solidly high for 'TTL'.
In this poorly specified realm, especially on products acquired through AlliBayZon, it's caveat emptor, though chances are everything will just work. This is OK for hobbyists, where failure is an option. Professionals will buy through proper channels, read data sheets, and won't get caught out.
