Lora stands for Long Range Radio. It uses spread spectrum modulation with low power transmitters.
TTN stands for The Things Network. TTN Lora gateways use this medium to transport Lora data.
It can be used for gathereing data from nodes. The nodes can have any sensor.
E.g. meteo data, pulution, water levels, GPS etc.
The range can be an area of aprox. 5x5km (3x3miles), depending on antenna/area conditions. See www.thethingsnetwork.org