Bluetooth LE and Bluetooth SPP are both Bluetooth profiles (sometimes called "pairing modes"). One practical difference between the two aforementioned Bluetooth profiles is the pairing process. Bluetooth SPP typically requires you to pair with the host operating system (through Bluetooth settings), then with the individual application (such as SerialMagic Gears or Cloud-In-Hand Mobile Grid). On the other hand, Bluetooth LE only requires that you pair with the individual application. Unlike Bluetooth SPP (which isn't supported on iOS devices; iPhones and iPads use Apple's proprietary profile Bluetooth iAP/MFi instead), the process for pairing via BLE is the same on iOS and Android applications.
Bluetooth SPP (Serial Port Profile) is intended to replace RS-232 cables (or other serial communication interfaces). SPP is excellent for sending and receiving bursts of data/information between two devices.
Bluetooth LE (also known as Bluetooth Smart or Bluetooth 4.0) is a significant release of the Bluetooth standard designed to optimize energy consumption and speed to work with extremely low power applications. Bluetooth Low Energy (BLE) also simplifies the user experience by circumventing the typical process of having to pair through the host device's Bluetooth settings before the application — with BLE the user need only pair through the application itself. However, this improvement does not come without some drawbacks; BLE sacrifices range to achieve faster speeds (up to 10 times faster than other Bluetooth profiles) and decreased energy consumption.
Click here to learn more about how to pair via Bluetooth SPP vs. Bluetooth LE.