20x4 LCD display is basic module and is very commonly used in various devices and circuits.20x4 LCD means it can display 20 characters per line and there are 4 such lines.
16x2 LCD display is basic module and is very commonly used in various devices and circuits.16x2 LCD means it can display 16 characters per line and there are 2 such lines..
This is Small SIM800L GPRS GSM Module Micro SIM Card Core Board Quad-band TTL Serial Port with the antenna.SIM800L GSM/GPRS module is a miniature GSM modem.