Historically, oil painting allowed artists to make more detailed and realistic representations of subject matter because of the slower dry time compared to tempera.  While this "technological advancement" was a pivotal point in the medium's history--oil painting has existed for as long as pigments could be suspended in oil.  There are paintings in the caves of Afghanistan that have been dated c. 650 AD that we think used poppy seed and walnut oil combined with natural pigments. 

There are three main categories of oil paints: traditional oils, alkyd oils, and water-mixable oils. These are all composed of pigment and binder. The binder encapsulates and protects the pigment, while it also acts as an adhesive by attaching neighbouring particles to each other. 

Once you decide on the oil you want to use, a solvent is usually the next choice point.  Solvent thins the paint to make it more workable and will not prolong drying time.  "Hazardous and odorous" are considerations for solvents and mediums.  You need to understand the hazards associated with the specific materials that you choose.   When working with most solvents you will need to be in a well ventalated area.  You will also need to learn how to clean up and handle the solvents at the end of the working sessions. You can not 'just dump them down the drain." 

Read this ARTicle by Winsor and Newton: Mythbusting Oil Misconceptions

Read this ARTicle on WikiHow: How to Oil Paint 

Read this ARticle by Blick Art Supplies: Oil Painting Advice for Beginners

Read over this list of oil painting vocabulary: A Glossary of Oil Painting Terms by ZenArtTeams

Look at over a dozen examples of oil paintings on Google Arts and Culture's "Discover Oil Painting."  Really though.  Click on at least 12 works of art, look at the art, look at the name of the artist and when it was created.  Note in your mind "this is what an oil painting can look like."