Light Tanks

Light tanks are first and foremost identified with a diamond.

I'm not going to go into specific details about every single light tank as each light tank has their own unique characteristics. You'll find more details about each tank from the WoT wiki. The link is at the side of this page.

What I am going to mention is the general characteristics of a light tank and their role.

General Description

As the name suggest, light tanks are very light in comparisons to their bigger counterparts.
They are fast and lightly armoured, making them very mobile and agile tanks.
They are small and have very good camouflage rating, that means they are harder to be spotted in bushes. They even maintain their camouflage value whilst on the move.
They generally have the weakest guns but are still capable of destroying other light tanks, medium tanks, tank destroyers and spg. Some light tanks are capable to do considerable damage to a heavy tank.

General Pros and Cons

Pros
-Fast and mobile
-Good camoflage
-Small size making it hard to aim from a distance.
-Good view range

Cons
-Weak armour
-low health
-Weak gun.

General Role
Scout (active/passive)

-Due to their small size, good camouflage value, fast speed and excellent mobility, they make great scouts.
-They could zip near enemy lines and quickly spot enemy movement and  quickly retreat before they  could be taken out.
-They could hide in a bush from a safe distance avoiding detection and spot passively for the team to eliminate those targets, earning you spotting damage.

 Things to remember 
-Always remember to be aware of your surroundings to prevent enemies from getting too close and spotting you, having Sixth Sense for your commander is highly recommended.
-Never be afraid to retreat at the first sense of danger
-Move in cover behind hills, bushes, trees, forested area or buildings.
-Cover and Concealment is a necessity.
-Stealth is your strength.
-Always use your speed and mobility to your advantage and make your movement unpredictable.
-Most tanks would find it hard to kill you if you run around them, especially the Heavy tanks and Tank Destroyers.
-You could even flank enemies and use hit and run tactics.
-SPG is your food, take them out when the opportunity arises, observe the enemy movements and wait for an opening before sneaking in for the kill. It will save your team from lots of trouble, giving your team an advantage.
-Always have good battle awareness, it's pointless if you can spot targets and keep them spotted but your team mates are too fair away or the enemy is not within clear line of sight.
-Never engage tougher tanks head on alone or otherwise. You'll die very quickly without doing much of anything. Wait for backup or retreat to safety.
-A dead scout is a useless scout, so stay alive!

Personal opinion for light tanks?
Personally I don't really like light tanks. It uses a totally different set of skills and mentality to have a good game using a light tank that I'm personally not used to. I'm not saying it's a bad tank. It's a great tank to have in a team if the person uses it well. It can be the most annoying tank to face if the tanker is a decent one. A friendly light tank can be the game breaker or the one that spoils your team chances of winning.

Imagine the situation of most of the enemy are dead and what's left are the slow tanks, they are aggressively attacking your base as your team mates are courageously defending it. You zip off to the undefended enemy base to capture. The enemy might try to retreat but that would leave their rear expose from your friendly tanks to kill or they just got too engaged in battle that they can't retreat safely. And you secure a win by capping.

Imagine the reverse, both teams are capping, you zip back to base to reset it (damaging a tank that is capping is enough to reset it's cap, so you don't have to kill it. Just use your speed to keep yourself alive and keep resetting it). What does it do? it buys your team time for a successful capture.

You run off early in the game to spot enemy tanks and your teams are spread out evenly across the map. You spot a huge force of enemy tanks going through one flank, relaying information to the rest of the team. Your team reorganizes their movement to counter the threat saving your team from a crushing defeat.

Light tanks may be seen as a weak tank but they are important. They are the "spy" or "ninja" of the team sneaking around, hit and run, relaying important information for the team to act on.

***Note***
Not all light tanks are meant for scouting, some are slow but heavily armoured and have to be played like a heavy tank. Some have decent firepower comparable to a medium tank and can be played as a medium tank flanking enemies for the kill or causing serious damage. Know your tank strengths and play accordingly. You can check the wiki for a clearer understanding of each individual light tank.