In Bromochlorofluoromethane (CHFClBr) the Carbon atom is designated as Chiral Carbon.
Chiral Carbon is that carbon to which four different atoms or group of atoms are attached. Chiral carbon is optically active center as its four groups occupies a specific region in space.
In this case,
Chlorine and Fluorine are present in the plane of the paper.
Bromine is behind the plane of the paper.
Hydrogen is in front of the plane of the paper.
Structure is as shown below,
