The unglamorous majority of the job
Real data arrives broken: missing values, duplicates, inconsistent formats, columns that mean different things in different rows. Wrangling is the patient work of fixing all that — gathering data from several sources, assessing its quality, repairing or removing what is wrong, and reshaping it into a tidy table. It routinely eats most of an analyst's time, and skipping it quietly poisons everything downstream.
It is the first real step of data analysis and the foundation under any machine learning model. In code it usually means tools like pandas in Python; at industrial scale it shades into data engineering.
Garbage in, garbage out
No model or chart can rescue bad inputs. Decisions made about how to clean and impute data shape the conclusions as much as any later analysis.
