句子成分（要具体的）

These是定语 people是主句的主语 后面是 定语从句 修饰 These people
其中 who 是关系代词 代替先行词These people引导定语从句 并作从句中的主语
often是从句中的状语
travel是从句中的谓语
to other countries是介词短语 作从句中的状语
can experience 是主句的谓语
something是主句的宾语 后面 是定语从句 修饰 something
其中that是关系代词 代替先行词 something引导定从 并作从句中 的宾语
they 是定从中的主语
have never seen 是定从中的谓语
before是定从中的状语.

These people是主语 who often travel to other countries 这是一定语从句修饰前面名词people. can experience是谓语 something 是宾语that they have never seen before也是一定语从句修饰代词something.

句子主干 These people can experience something

定语从句 who ofthen travel to other countries 作定语，修饰先行词these people

定语从句 that they have never seen before 作定语，修饰先行词 something

These people主句主语 who定语从句主语 often从句状语 travel to从句谓语 other countries从句宾语 can experience主句谓语 something主句宾语 that第二个定语从句的宾语 they 二定主语have never seen二定谓语 before二定状语.

These people主语 （who often travel to other countries 定语从句修饰people） can experience 谓语 something 宾语 （that they have never seen before 定语从句 修饰something）.