The order of layers in the Table of Content affect how the features show up on the map. Features in top layers, would cover features in bottom layers. It’s generally recommended to put point and polyline layers on top of polygon layers to avoid any cover-up.
To move the layers in Table of Content, select the layer first and drag it to the new location. Moving a group layer will also move all children layers.
Layers can all be moved by using the Move Layer Up and Move Layer Down context menu. Layers in a group layer can only be moved inside that group.