General Information:

Jesus and his disciples go up to Jerusalem to the temple.

went up to Jerusalem

This indicates that he went from a lower place to a higher place. Jerusalem is built on a hill.

The next verse makes it clear that these people are in the temple courtyard. That area was intended for worship and not for commerce.

People are buying animals in the temple courtyard to sacrifice them to God.

Jewish authorities required people who wanted to buy animals for sacrifices to exchange their money for special money from the "money changers."