The tall trees look like a roof over the other plants in the forest is called as

The tall trees look like a roof over the other plants in the forest is called as canopy.

Crown of the trees is the top portion of the tree which includes branches, twigs, leaves, fruits and buds. It has the important job of making food for the plants. Since the crown of a tree looks like a roof or a cover over the other plants, or the crown of many trees appear to be a roof over the forest floor, hence, the term canopy, which is derived from the Latin word 'conopeum' meaning ‘mosquito net/cover over a bed’.

Note: Crown is used for individual tree, canopy is the layer of forest used for crowns of many trees.