Column ties are the starting point of most Shibari ties. "Column" is to be taken literally: an arm is a column, a leg is a column. Generally speaking, column ties are §bowlines.
Column ties are classified by number of columns:
Note that a single-column tie around two arms is still a single-column tie - the double-column is a different form, not just the same form tied around two columns.
Different column ties are either §forward or reverse tension - this is an important property of the tie.
Most column ties are tied in the end of the rope. Column ties in the middle of a rope (e.g. to bind a second limb) are called §inline column ties.