What does Refresh in the dropdown windows menu means?

There is a link between your computer and the host that you are connected to.

Each machine 'talks' to the other confirming their presence and any choices you may pick on your screen.

If you spend a long time on one screen and your mouse activity is zero, the page that you are looking at becomes a 'picture' of the screen that you last received, almost trapped in time.

Refresh brings the content of the page back into the 'present' - bang up to date.

So if you click on a screen choice after a period of inactivity, refresh brings the two computers back into sync with each other: if you click without refresh the delay is caused by the computers updating before your choice is enabled.

Refresh is best used on 'net pages that are likely to have changed values in the time that you have spent reading it.

If you are browsing a network share displaying the contents of a folder.

THe contents can change. Especially if the folder is shared between multiple users. Files are added,deleted and changed.

Refresh tells the program to re-read the directory to make sure the information is up to date and accurate.