active field
Computing term for the currently selected or editable field in a user interface, such as a text box or form element.
タブキーで次の動作フィールドに移動できます。
You can move to the next active field with the Tab key.
Compound of 動作 (どうさ, 'action' or 'operation') and フィールド ('field'), a direct translation of the English computing term 'active field'.