What is a linear meter?
This isn't just for fabric, but carpet and all sorts of material on rolls. A linear metre simply means 1 metre length off the roll. It says nothing at all about the width, which is usually more than a metre for fabric, but for some things may be much less.

The width should be specified elsewhere in the description, to allow you to calculate how much to buy. You are likely to need to take more into account than the total area, for all but the simplest project with plain fabric.