Why use process statement in vhdl?

Almost all programming languages are sequential in nature. But VHDL is a concurrent language. In an architecture for an entity, all statements are concurrent. So where do sequential statements exist in VHDL?. There is a statement called the process statement that contains only sequential statements. The process statement is itself a concurrent statement. A process statement can exist in an architecture and define regions in the architecture where all statements are sequential. A process statement has a declaration section and a statement part. In the declaration section, types, variables, constants, subprograms, and so on can be declared. The statement part contains only sequential statements. Sequential statements consist of CASE statements, IF THEN ELSE statements, LOOP statements, and so on.