Arduino MEGA 2560 is an extended version of Arduino UNO. It is mainly for more complex and larger projects.
It has 54 digital I/O (input/output) pins. From that 54 digital pins, 15 pins can be used as PWM outputs.
It has 16 analog pins and a big space for your sketch. It is a suggested board for 3D printers and robotics.
Arduino Mega is based on Atmega2560 microcontroller with 256 KB flash memory and 8 KB SRAM

Arduino Mega Pinout

Technical Specification
Microcontroller | ATmega2560 |
Operating Voltage | 5V |
Digital I/O Pins | 54 (of which 15 provide PWM output) |
Analog Input Pins | 16 |
DC Current per I/O Pin | 20 mA |
DC Current for 3.3V Pin | 50 mA |
Flash Memory | 256 KB of which 8 KB used by bootloader |
SRAM | 8 KB (ATmega2560) |
EEPROM | 4 KB |
Clock Speed | 16 MHz |
LED_BUILTIN | 13 |
Length | 101.52 mm |
Width | 53.3 mm |
Weight | 37 g |