Apple to release two versions of iPhone named iPhone 5S and iPhone 5C. The 5C will be cheaper than 5S. you can read a small comparison below
iPhone 5S
A7 chip with 64-bit architecture
M7 motion coprocessor
Fingerprint identity sensor
16GB, 32GB, 64GB
Height: 4.87 inches (123.8 mm)
Width: 2.31 inches (58.6 mm)
Depth: 0.30 inch (7.6 mm)
Weight: 3.95 ounces (112 grams)
Camera - 8 megapixels with 1.5µ pixels , ƒ/2.2 aperture, True Tone flash, Burst mode
Available colors - silver, gold, and space gray
iPhone 5C
A6 Chip
Will NOT have M7 motion coprocessor and Fingerprint identity sensor compared to 5S
16GB, 32GB
Height: 4.90 inches (124.4 mm)
Width: 2.33 inches (59.2 mm)
Depth: 0.35 inch (8.97 mm)
Weight: 4.65 ounces (132 grams)
Camera - 8 megapixels, ƒ/2.4 aperture, LED flash
Available colors - White , Pink, Yellow, Blue, Green
Both phones will have
4-inch (diagonal) Retina display with 1136-by-640 resolution and 326 ppi
30fps, 1080p HD video recording
You can compare the iPhone 5S and iPhone 5C with iPhone 4S here