Tartan comes from Scotland. More than 1000 years ago, families were called clans. Each clan had a tartan, their own pattern for dress. Men wore kilts, like skirts. You can read more about the history of kilts here.
http://www.lords-n-ladies.com/kilthistory.htm

Nowadays, there are hundreds of types of tartans. You can see them here.
http://www.house-of-tartan.scotland.net/house/tfinder.htp
You can find tartans by name or colour.

Famous clans include McLeod, Campbell and McDonald (just like the restaurant!). 'Mc' means 'son of'. So McDonald is the son of Donald.

Scottish men still wear kilts at weddings and other parties. Here is a website selling kilts.
http://scottishkilts.net/ They are very expensive, over HK$3000 each!

Tartan is used to make hats, scarfs, skirts, miniskirts, ties, handbags and trousers nowadays. This website has good examples.
http://www.house-of-tartan.scotland.net/products/select.htm

Here are some pictures of fashionable uses of tartan.
http://www.house-of-tartan.scotland.net/news/fashion-show.htm