# ROOT Manual - Functional parts

In the second part of the ROOT Manual, numerous application areas and special topics of ROOT are presented.
The Trees chapter describes, how the data from LHC (Large Hadron Collider) experiments are stored in trees and ROOT files. In chapters like Histograms, Dataframes, and RooFit is explained, how you can visualize and analyze the data with ROOT.

The second part of the ROOT Manual contains:

• Histograms
Histograms are approximate representations of the distribution of numerical data and they play a fundamental role in any kind of physical analysis.

• Graphs
A graph is an object made of two or three arrays X, Y and Z holding the x,y and z coordinates of n points.

• Graphics
ROOT provides powerful graphics capabilities for displaying and interacting with graphical object like plots, histograms, 2D and 3D graphical objects, etc.

• Fitting
Fitting is the method for modeling the expected distribution of events in a physics data analysis.

• Dataframes
With RDataFrame, ROOT offers a modern, high-level interface for analysis of data stored in TTree s, CSV files and other data formats, in C++ or Python.

• Trees
Trees can handle large columnar datasets.

• RooFit
ROOT provides with the RooFit library a toolkit for modeling the expected distribution of events in a physics analysis.

• TMVA
The Toolkit for Multivariate Data Analysis with ROOT (TMVA) provides a machine learning environment for the processing and evaluation of multivariate classification.

• Python interface: PyROOT
With PyROOT, ROOTâ€™s Python-C++ bindings, you can use ROOT from Python.

• Mathematical libraries
ROOT provides a rich set of mathematical libraries.

• Physics vectors
ROOT provides several packes for physics vectors.

• Geometry
A geometry represents a Hierarchie of constructive solid geometry primitive elements (shapes or solid).

• I/O concepts
An overview of several important concepts and features related to reading and writing data.

• I/O of custom classes
Reading and writing arbitrary C++ classes.

• Signal/Slot communication
ROOT supports its own version of the signal/slot communication mechanism.

• JSROOT
JavaScript ROOT (JSROOT) provides interactive graphics in the web browsers.