The traditional method of making a cup of tea is with loose tea placed either directly, or in a tea infuser, into a tea pot and pouring boiling (or very hot depending on the type of tea) water over the tea. In the second half of the 20th century the use of teabags has largely supplanted the use of loose tea in the western world; this has enabled brewing directly in a cup or mug.
Iced tea is a form of cold tea, often served in a glass over ice. Any variety of dry tea may be iced, according to one's tastes. All one has to do is brew the tea and then chill it, or purchase a pre-bottled or -canned tea.