Going back to the serial RS-232 standard, there are a number of configurations for how many serial bits are sent at once. But with TTL serial, it is pretty standard that software is set for 8 bits, no parity bit, one stop bit, abbreviated 8,N,1 or 8, 1, N.
A key parameter for setting up serial communications is setting a baud rate. Best to think of it as how many bits a second are transmitted. Typical speeds follow old-time modem rates such as 1200, 9600, 19200, 57600, 115200. 256000, and 1 megabit. While setting non-standard rates may be possible with software serial, hardware may only accept fixed rates. For microcontrollers, 9600 is a typical slow rate and 115200 often a fast rate. Check your hardware specifications (spec) sheet for the baud rates the board supports.
When you run your terminal emulator, you'll need at least the baud rate, possibly the bit configuration also. Below is the configuration you might set up for Windows PuTTY:
Note the Serial line box has the COM port name, and Speed has the baud rate. We also have to click the Serial radio button to make sure we have a Serial connection
While your final project may have two devices communicating without any visualization on what is being exchanged, viewing serial communications is very common. It was the primary way to interface with minicomputers before PCs came along.
Serial communications software has many names but they all basically do the same thing: display the outgoing data as characters and possibly allow the user to send characters back.
Mac and Linux
Linux and the Mac command line have the terminal capability to initiate serial communications. See our guide Advanced Serial Console for Mac and Linux for more information
Windows does not have a serial terminal standard but there are many third party terminal emulators including PuTTY and Tera Term among others. See our guide Advanced Serial Console on Windows for more information.
Your Windows COM port will be shown in the Control Panel -> Devices and Printers section, under Unspecified Devices and names Silicon Labs CP210x USB to UART Bridge.
Use that COM port and the baud rate in your code for your terminal software