Use of "of "

[Mauricio67]

Please,
What's the explanation of:

. Minister of transportation or Transportation Minister?
. A cup of glass or a Glass cup?

My students ask me how to use it ,and I'd like to know how to.

[colloquium]

Please,
What's the explanation of:

. Minister of transportation or Transportation Minister?
. A cup of glass or a Glass cup?

My students ask me how to use it ,and I'd like to know how to.

Minister of transportation

Here of means connected or associated with.

The Minister associated with the transportation department.

Transportation Minister

This is an official title. It can be further described as a compund noun.

A cup of glass

Here of (meaning containing in this context) should be followed by what is in the glass.

A cup of water/sand/flowers.

to explain the material which the cup consists of (glass) you should use made of.

A cup made of glass.

a Glass cup

The adjective glass explains which material the cup is made of.

Adjective+noun

a yellow car

a wooden chair

I'm not a teacher.