Abstract
A brief overview of what the article is about and why the authors did the experiment.
Introduction
Gives you the motivation and importance of the study, includes background information.
Methods
How the experiment was carried out. You need to see the general method and processes used.
Results
This is the raw data from the experiment. There will be charts and tables. Understanding the charts and tables is very important for understanding the paper.
Discussion
Also called analysis or conclusions - learn the reasons for the conclusions. This is where you test if you agree with the logic of the conclusions. Using this and the abstract you can determine if the article is relevant to your research.