Overview
A parliamentary leader is a political title or a descriptive term used in various countries to designate the person leading a parliamentary group or caucus in a legislative body, whether it be a national or sub-national legislature. They are their party's most senior member of parliament (MP) in most parliamentary democracies.
A party leader may be the same person as the parliamentary leader, or the roles may be separated.
Terminology
In many countries, the position of leader of a political party (that is, the organisational leader) and leader of a parliamentary group are separate positions, and while they are often held by the same person, this is not always or automatically the case. If the party leader is a member of the government, holds a different political office outside the parliamentary body in question, or no political office at all, the position of parliamentary leader is frequently held by a different person.
In English, the leader may be referred to as a "parliamentary chairman", "group leader" or simply "parliamentary leader", among other names.
From Wikipedia (CC BY-SA 4.0).