It seems something needs to be clairified here.
As well something I haven't been through yet. And that's all the TANKS, driving around on the battlefields. In the game, exists five different classes of tanks. Lights, mediums, heavies, tankdestroyers and artillery.

Most of the lights gets the role of scouts.
(♦) All tanks marked with this icon in the top of your screenpicture on the battlefield, are light tanks. Lights have no armor, and they are also lower in weight-class than the other tanks. The role of those tanks are to get out, spot enemy vehicles, track them and DISTRACT them so the allies can take them down.  The longer a scout can manage to stay alive in battle, still active, the more benefit, can the team get out of it.
Now, scouting, is not just to drive around. The task is parted in passive, and active scouting. Passive scouting is to find a good bush, be fast enough, that no enemies will spot this scout getting there, to spot them. Doing this, the scout/spotter, will get 50% of the experience, the teammates gets for getting oponents down, just by spotting the targets.
Most scouting drivers use passive scouting in the start of the battle, to get enemies spotted. Once the first enemies are down, it's time to get moving, to active scouting. Several videos can explain more about it. One aspect of this active scouting, is that you never peak out the same spot twice in a row. If you do so, your target will be ready and waiting for you, and you're destroyed, toasted dead "meat".

The next class is the medium tank(//). Some mediums are allround tanks. decent guns, most of them, bit thicker armor, ok view-range and decent speed for most of them. They can support heavies, tankdestroyers, lights. They can do everything. But medium tanks are stronger the more they are together. That's a common fact, for most tanks in the game, if they work together, they can achieve even more. Because of the still not so thick armor of the mediums, you will have to think in flanking manouvres, and get flanking fire in on the enemy team, before they rip your team's maybe heavies, facing off their heavies. Best thing to experience as a medium is when you can sneak off shots, from behind the corner of the hills being their assumed safe postion, and shot by shot take them down. 

The next one is the heavies(///) Most of them are more other less brawlers. They fight on the front lines, against enemy heavy-tanks. Now, some heavy tanks, are only heavies, "ON THE PAPER". They literally have no armor at all. Here is French heavies the brightest example. Each heavy has it's benefits/quaities and limits. As player of a heavy tank of each nation, you have to learn, understand and not to mention, USE, this knowledge. On the maps as you fight. Use terrain, bushes and obsticles as concealment, and cover to hide at least, your weakspots. Angle the tank around corners, due to trick the enemy to fire a shot off too early, and use his reloading time against him.
Heavy tanks with softer/thinner armor, are played as medium tanks.

Then we have the tankdestroyers. They're marked with an upside-down triangle in the line of icons. Their role is mostly to sit back on the map and deal damage on distance to enemy tanks. Most of the tankdestroyers don't have very much armor, but extremely powerful guns. The role of those vehicles is sniping. You can call it camping or what ever you want, but tankdestroyers are meant to DESTROY TANKS, in distance and protect artillery.

What all tanks have in common though, being bottom tier on the line-up, doesn't mean "camp at the back", or "suicide" whether playing light, medium or heavy tank. It means "be careful, have attention and play causiously". Your team can still use the firepower of your gun, and the viewrange you still have. You can provide your team with eyes, staying just below the ridgeline of a minor hill, they can use your eyes, if you surfe the ridgelines of hills, just pointing your gun up and quick back to cover. They can use your ammo, tracking the enemy, and perma tracking them, pinning them in place, for artillery to take them out. Once the OP superheavies, are out, you have that one less to worry about and becomes more free to do more to the outcome of the battle.

Last, but not least, there is the artillery. It's hated by a lot of players out there. Some, even to a degree, where they go teamkill it, the very second the battle begins. But sometimes, and some replay videos on YouTube are great and clear proof of that, taking out the artillery, can mean taking out the chance to win. The challenge for artillery, is different, than to other tanks. Low tiers and British artillery have a short firing arch compare to others. To reach on a certain position, you will have to move closer. The role of artillery, is to support the team on distance. But there are positions where even the artillery can't reach. The trick to stay alive longer here, is to relocate frequently on the battlefields, if best, after and between every shot. It's not necessary to move far. Just enough, for you not to be hit, splashed or effected in other ways, by the enemy team's artillery. Should you have further interest in learning more, I can refer you, when it comes to artillery at least, to the group on facebook, WOTArtyNoobs. In there, they know a lot of artillery and they can even help you with skills and perks on the crew, when you get so far in your grinding process.