A more thorough explanation:

Suzereign is another spelling of the word suzerain. A suzerain is a term used in international law to describe a nation that has control over another nation's foreign relations. In history, it also referred to a Crown tenant, who held an estate immediately of the Crown.

One example of a suzerain relationship is China's relationship with North Korea. China is considered the suzerain of North Korea because it has significant control over North Korea's foreign relations.

In medieval Europe, a suzerain was a lord who granted land to a vassal in exchange for loyalty and military service. The vassal was known as a suzerain.

The examples illustrate the two different historical and modern uses of the term suzerain. In the first example, China is the suzerain because it has control over North Korea's foreign relations. In the second example, the suzerain is the lord who grants land to a vassal in exchange for loyalty and military service.