A hockey jersey is a piece of clothing worn by ice hockey players to cover the upper part of their bodies. They also are worn by fans to show support for a team, or to create ties to a hometown or region.
"Hockey sweater" is a term originating from the sport's earlier days when it was predominantly played outside during winter and when the sweaters worn by players were warm, wool-knit coverings. This term has fallen out of common usage since the switch to polyester.