Camouflage is an important part of the spotting mechanics of World of Tanks Blitz, it defines how easy or hard it is to spot tanks, these values are different for each tank. There are various things that will affect your camouflage rating; camouflage pattern, camouflage net, camouflage crew skill, etc.
Each tank has three standard camouflage values; when the tank is stationary, when it's shooting and when it's moving. On light tanks, the camouflage values when moving and stationary are the same, making light tanks one of the hardest vehicle types to spot.
Your loadout can help you increase your camouflage values, thus remaining unspotted from closer stances and for longer periods of time. As mentioned before you can equip camouflage patterns on your tank. These grant different concealment bonuses depending on the tank type you apply them on. Heavy tanks get 2% bonus, Lights and Mediums get 3%, and Tank Destroyers get 4%. You can also equip a camo net to improve this number even more, it's worth mentioning that the camo net only works when your tank has been stationary for 10 seconds. Every time your tank moves, you lose the bonus, however if you only move the turret the bonus will remain.
It's also worth mentioning that there are more variables that affect your concealment, for example the Camouflage crew skill which improves your concealment levels permanently. It is a tank destroyer skill and one of the most important skills period. It can improve your concealment up to 18% if you train it at level 6. Bushes and fallen trees also increase your concealment level considerably.
One of the best concealment loadouts in the game is: Using a low profile tank (StuG, Borsig, E 25, etc), applying a camo pattern + camo net + camo skill + staying behind a bush + bincoulars (in order to spot enemies before they spot you).