It should be a representation on some dimensions of the people that elect them, but on others it generally should not.

For example a country with multiple significant ethnic groups should probably have a parliament with a similar ethnic split. A country with a significant rural population and a significant urban population should probably have a similar split in parliament.

Within those groups people are going to vote for their best people for the job. That's generally going to be from among the smarter and/or more educated in their group.

That results in a parliament that is not representative along those dimensions.