basic tent help

A 3 season tent usually means it is designed for use during Spring, Summer and Fall weather. Where a 4 season tent is intended for the previous 3 seasons plus Winter use.

It is kind of relative to where you are using it though. So just think of the 4 season tent as something that should be ready for cold weather and snow. 4 season tents ofter weigh more.

Are 4-season tents then made of different material to make them warmer?

Perhaps a better term for "4 season" tents would be "4th season" tents. Generally speaking, if a tent is truly designed for harsh winter conditions, then it is probably poorly suited for summer.

Double walls (not mesh) create somewhat of a temperature gradient between the outside and you. Several crossing poles provide strength to resist high winter winds, especially in exposed areas. They also can support snow loads on top of the tent. The shape, sloping walls, helps shed snow while making interior space less efficient. And, of course, all this comes with a weight penalty.

Personally, I would take a different tent in summer with lots of bug netting, venting, vertical walls with flat roof to give lots of room and lightweight.

I pretty much agree with Michael on this. I use a tarp or a TarpTent except in the dead of winter. When heavy snow loads and high winds are possible I carry the extra weight and use a tent designed for that purpose. Care must be taken to still allow plenty of ventilation, even at the cost of warmth, or condensation will form in even the very best double walled winter tent.

"I now see the light!" Thanks for the explanation.

Subscribe to BPL and read this article:
http://www.backpackinglight.com/cgi-bin/backpackinglight/when_things_go_wrong.html

Then you will understand the difference!

Cheers