Describes something unadorned, without unnecessary decoration or complexity; often used for lifestyles, designs, or systems that are intentionally restrained.
He leads a simple life.
This room is plain and calming.
The company simplified the procedures.
He left the city and now leads a simple life.
The wedding was held as a simple ceremony.
簡素 describes something plain and minimal, contrasting with 凝った, which describes something richly detailed or fancy.