Just what is science fiction? If I pick up a science fiction story or novel, will I be able to understand it? Will it be so full of science and logical thinking that I will not have any idea of what is going on within the story?
Rest assured that you do not need to worry. One reassuring fact is that often science fiction deals with current science and technological issues. It usually deals with it a way that helps us to understand some of the possible impacts of those issues and trends.
Another reassuring thing is that science fiction literature has the same basic elements that other literature contains. These elements (or characteristics) are storyline, frame, characterization and pacing.
Storyline is the "what is this about?" question and answer. Think of it as the topic, or the plot, such as nuclear war in Nevil Shute's "On the Beach," or robots (technology) in Karel Capek's "R.U.R." or Isaac Asimov's robot novels and stories. Science and technology usually play a large role in science fiction stories, thus the name "science" fiction.
Frame is the setting, the "where and when is this happening?" question and answer. The stories are usually set in the future, as seen from the vantage point of the author of the story. Sometimes this is the relatively near future, as in Kate Wilhelm's "Where Late the Sweet Birds Sang" and "Juniper Time," or Edward Bellamy's "Looking Backward." Other stories are in a more distant future, like H.G. Wells's "The Time Machine." The answer to the where can range over the entire universe, from the Earth of Clifford D. Simak's "City," to Milky Way Galaxy-wide stories, as in the various Star Trek tales, to out of our galaxy tales such as the Star Wars series of stories. Stargate SG-1 stories have Earth-based humans interacting with issues on Earth and universe-wide. Science and technology form a strong part of the setting, too, often involving space or time travel, medicine, biology or any other science field you can imagine.
Characterization is the "who" of the story. Science fiction has, overall, had less in the way of character development than other types of literature. The science and technology is often the point of the story, with people there to help the science and technology move forward in the story. In a sense, science is one of the characters, and is often better developed than the individuals who are acting out the story.
Pacing is the movement of the story, sort of the "how and why?" questions. If the action is coming from within a character, the speed of the story will be a bit slower than if a lot of the action comes from outside. The "storyteller" type of science fiction will pose an issue, and often offer the solution during the telling of the tale. There is more action, more outside interaction, and often more in the way of "hard science" (but with this last, that is not always the case). Asimov, David Brin and Orson Scott Card's works are often termed "storyteller style." The "philosophical style" has more internal-focus in the story, more character development, and moves at a slower pace than the storyteller style.
One thing of note about science fiction is that it has often been able to make thoughtful commentary about current issues by placing them in an alien (either in place or time) context. Therefore, anything that may be seen as "preachy" if set in a completely contemporary and familiar setting can be carried out, and we can see what the effects of different technologies and issues may or might really be in an entertaining way.
http://www.conknet.com/~fullerlibrary/ReadersAdvisor y/SCIENCE%20FICTION%20READER/Introduction.htm
http://www.sacramentopress.com/headline/243/What_is_ a_storyline
http://www.readwritethink.org/lesson_images/lesson27 0/genre_sheet.pdf
http://engla.jppss.k12.la.us/writing%20craft%20&%20genre%20instruction%20files/the%20characteristics %20of%20science%20fiction.pdf