Explain why multicellularity of an organism requires cell-to-cell communication. and, what is the word that means “within the cell,” such as referring to signals moving from one place to another within the cell?

In multicellular organisms, cell communication is vital. Cells communicate through chemical and mechanical signals and this is the cells way of survival--they receive and process information from the external environment. Multicellularity of an organism requires cell-to-cell communication because through this, different cell types can cooperate together to function and join to form different tissues and organs in the body. 
In addition, the word that means "within the cell" which refers to the signals moving from one place to another within the cell is the term INTRACELLULAR.

Sorry  i don't understand can you rephrase that