Data Analysis is the process of acquiring, processing, transforming, modeling and analyzing the large dta sets to get something out of the data.
This is the process of acquiring the data from various sources and then moves it to the Big Data Platform (for example Hadoop cluster). Make sure that the data being collected is correct and with less error.
This is the process of processing the collected data and save it into easily analyzable format. For example you may process the data and store it not rows and columns for easily access.
This is process of validating and correcting the data. For example if data is duplicate then remove the duplicate data. If data is missing try to get the correct data again etc?
Once the data is cleaned it is ready for analysis and various analysis methods are used for the analysis of the data in Big Data environment. Data visualization is also part of data analysis and good visuals and meaning full report is the heat of any data analysis as the final goal is to get some report to make business decision.
Check Big Data tutorials.