The Galaxy A Series is a 2017 lineup of budget phones from Samsung.
The feature that these phones all have in common is the Exynos 7880 chipset with an Octa-core 1.9 GHz Cortex-A53 CPU. Other than that, each device has slight changes in their specifications.
The A7 is the largest of the three phones. With a 5.7" 1080x1920 display, you will have 3GB of RAM and 32GB of storage. A 3600 mAh battery can be charged via the USB type C port. Both cameras get equal attention on this device as they are each equipped with 16MP sensors.
The A5 is the mid-range phone on this lineup. The 5.2" screen has a resolution of 1080x1920. The same 3GB of RAM and 32GB of storage is featured in this phone as well. 16MP cameras are mounted in both the front and the back of the device, being powered by a 3000 mAh battery.
The A3 is the smallest device in the 2017 lineup, with a 4.7" 720x1280 display. A smaller 2GB of RAM and 16GB of storage are packed into this phone. The back camera has a 13MP sensor and the front is equipped with 8MP. The type C connector on this phone will be used to charge the 2350 mAh battery.