Team Fortress 2 Question Please Respond

I was playing TF2 for quite some time, you may die fast but sure is fun.

I have noticed that opponents and team members having different weapons form what I have for each class. Then I notices that some people have like a "level 10 flamethrower" and such, going through my main menu, all my weapons are level one. I also seen a Pyro using a flare gun, something I don't have.

How does the weapon system work? Do weapons change with added use? How do I get additional weapons like the Pyro's Flare Gun and Sniper's Bow?

Where in the levels do I find things like the "Sandvich" for "Boxing Gloves"?

There are two methods of getting new items: One is getting milestone achievements (Which are earned by getting X achievements for that class.) or by simply playing enough until you're randomly awarded the item.CaelCyndar

Hey guys do the levels of the weapon mean anything?

I have been getting weird items like level 59 dead ringers lately.