As basic as this may seem there is a standard look and criteria of description for a tree in general; by definition a tree reaches a minimum height of three meters having the trunk diameter of at least thirty centimeters. Other woody plants that don't fit these standards, like those which have multiple stems, are generically called shrubs. Trees live the longest on our planet, and it is said that the oldest tree in the world is more than five thousands years old.
A tree plays plenty of function in its immediate environment, it prevents erosion defending the ecosystem it lives in by soil fixation, and then it plays an important role in the air purification process as leaves absorb the carbon dioxide while releasing oxygen. The forest is also responsible for temperature moderation acting like an oasis of fresh air and triggering rain formation.
From an economic point of view the wood industry relies on trees, they are the raw material for any wood object. Until the 19th century the entire building industry was based on wood, in those days good essences like oak were held in high esteem and they are easily comparable with steel these days. To give just an example for the importance of wood: until the twentieth century the navy was one hundred percent dependent on quality wood and any tree represented valuable primary matter for ship building.
Explorers have been looking for the tallest tree in the world for a long time particularly since tradition tells us about trees that have reached 150m. Considering the methods used to measure tree size, most scientists reject such figures as being unreliable. It was concluded that using the old measuring procedures an error of maximum 15% more or less could result. At present the tallest tree is a Sequoia sempervirens which reaches the height of 115.55 meters, the tree grows in the United States, California, Redwood National Park.
The stoutest tree is a Taxodium mucronatus which reaches 11.6 meters in diameter, and it is located in Oaxaca, Mexico. There are plenty of stories circulating about the incredible size trees reached in the past, nevertheless evidence lacks to support such speculations. Even Charles Darwin spoke about a trunk which had 40 meters in diameter but many take the story as an anecdote and not as scientific truth.
The oldest tree is even more difficult to find as determining the exact age relies more on speculation than on science; using all possible techniques it has been concluded that the oldest tree is a Pinus longaeva with an age of 4844 years. Yet the measurement remains uncertain and is susceptible to errors. Trees have always been the symbol of longevity, this is why many cultures use them as an epitome long life expectancy.