What is the real life application of tree data structures?

Folders in Operating system:

in windows go to command line and type tree. You can see the folder tree structure.

Linux file system is also a tree.

HTML Document Object Model (DOM):

All html text,attributes are stored in tree called Document Object Model (DOM).

Network Routing :

Syntax Tree in Compiler :

In compiler , every expression is converted into syntax tree format.

Auto correcter and spell checker :

Next Move in games:

In Artificial intelligence game (opponent is cpu) , next moves are stored using tree data structure.

• Binary Search Tree - Used in many search applications where data is constantly entering/leaving, such as the map and set objects in many languages' libraries.
• Binary Space Partition - Used in almost every 3D video game to determine what objects need to be rendered.
• Binary Tries - Used in almost every high-bandwidth router for storing router-tables.
• Hash Trees - used in p2p programs and specialized image-signatures in which a hash needs to be verified, but the whole file is not available.
• Heaps - Used in implementing efficient priority-queues, which in turn are used for scheduling processes in many operating systems, Quality-of-Service in routers, and A* (path-finding algorithm used in AI applications, including robotics and video games). Also used in heap-sort.
• Huffman Coding Tree (Chip Uni) - used in compression algorithms, such as those used by the .jpeg and .mp3 file-formats.
• GGM Trees - Used in cryptographic applications to generate a tree of pseudo-random numbers.
• Syntax Tree - Constructed by compilers and (implicitly) calculators to parse expressions.
• Treap - Randomized data structure used in wireless networking and memory allocation.
• T-tree - Though most databases use some form of B-tree to store data on the drive, databases which keep all (most) their data in memory often use T-trees to do so.
  
  BTree : we use BTree in indexing large records in database to improve search.