Blocks are transparent. When we try to jump and there is a block exactly above us we dont colide instead we go into take damage and come back again. The picture i uploaded contains iron block above my head.

My device : yu phoria

Update by Mega_Spud:

It's possible to walk into solid blocks sometimes after flying with Elytra equipped.

Steps to Reproduce:

• From a height, fly down with elytra into a body of water
• Walk into a 1 high gap
• Notice your head can clip into a solid block
• If you do this in survival you will take suffocation damage

Video demonstration: https://youtu.be/I2Oq8aWxwzU