Referring to an element:

<xs:element ref="my:name"/>

The attribute 'minOccurs' specifies the minimum number of these child elements (default is 1).

The attribute 'maxOccurs' specifies the maximum number of these child elements (default is 1).

<xs:element ref="my:name" minOccurs='2' maxOccurs='5'/>

This says: "element 'my:name" can occur between 2 and 5 times here."

The attribute 'maxOccurs' can have the value 'unbounded.

<xs:element ref="my:name" minOccurs='2' maxOccurs='unbounded'/>

This says: "element 'my:name" can occur 2 or more times here."

Examples in context:

<xs:element name="people">
  <xs:complexType>
     <xs:sequence>
        <xs:element ref="my:name" maxOccurs="unbounded"/>
     <xs:sequence>
  </xs:complexType>
</xs:element>