Serial.readBytesUntil() reads characters from the serial buffer into an array. The function terminates if the terminator character is detected, the determined length has been read, or it times out
Serial.readBytesUntil(character, buffer, length)
character: the character to search for (char). buffer: the buffer to store the bytes in (char[] or byte[]). length: the number of bytes to read (int). byte