What are the differences between 50i and 50p?

For PAL region:
The differences between 50i and 50p.
50i records 50 frames per second using the interlace scanning system, and 50p records 50 frames per second using the progressive scanning system. 50i is recommended for normal recording.

The interlace scanning system reads even-numbered and odd-numbered scanning lines alternately. Meanwhile, the progressive scanning system reads even-numbered and odd-numbered scanning lines simultaneously thus it has double information per unit time compared with the interlace scanning system.