What does it all mean?

For some reason or other I found myself on the WPP website today.

Curiosity got the better of me and I clicked on the Y&R link.

This opened a page listing about 100 office worldwide.

No surprises there.

The weird thing was each of them was listed as 'Full Service Advertising'.

Full service advertising - What does that mean exactly?

And if you do know what it means, is it still a relevant term in the 21st century?