The Model A+ is the low-cost variant of the Raspberry Pi. It replaced the originalModel A in November 2014. Compared to the Model A it has:

• More GPIO. The GPIO header has grown to 40 pins, while retaining the same pinout for the first 26 pins as the Model A and B.
• Micro SD. The old friction-fit SD card socket has been replaced with a much nicer push-push micro SD version.
• Lower power consumption. By replacing linear regulators with switching ones we’ve reduced power consumption by between 0.5W and 1W.
• Better audio. The audio circuit incorporates a dedicated low-noise power supply.
• Smaller, neater form factor. We’ve aligned the USB connector with the board edge, moved composite video onto the 3.5mm jack, and added four squarely-placed mounting holes. Model A+ is approximately 2cm shorter than the Model A.

We recommend the Model A+ for for embedded projects and projects which require very low power, and which do not require Ethernet or multiple USB ports.