As there is no universal official definition, the following is just approximate.
A brick is typically made of clay, slightly pressed in a mold, and then burned. So most of the times it will have a reddish color. There are also "stabilized earth bricks". They are normally made of a soil that contains some clay. Ideally they shouldn't contain any organic matter. To keep this brick in shape, it is not burned but "stabilized" (hardened) with cement or lime (lime reacts with clay to form a simple cement).
Tiles might have about any size, but are very flat, as they are used to cover surfaces, like floors, bathroom walls, etc. A good tile is made of pure white kaolin clay (very abundant in China). It is also burned, just like a brick, though more care is taken to keep it in shape, conserve the desired color, etc.
Blocks are normally made of gravel and sand with some cement, and can be about 15x20x30 cm in size. Most of the times the cementitious mix is pressed in a mold and then steam-cured, to speed up the hardening. Also you will typically see that the block is hollow, with a "bridge" dividing the 30 cm length in half.