Do the letters ol in a substance only indicate that the substance is an alcohol if they came at the end of the name of a substance? Do the letters ol if they are together only indicate the substance is an alcohol if they come together at the end of the name of a substance? for example,is glycerol an alcohol because the letters o and l come together at the end of its name and olives and olive oil are not alcohols because the letters o and l do not come together at the end of any words in their names?
Yes, the ending ol in a name is a good hint that the compound contains an $\ce{OH}$ group.

However, beware of trivial names: 


$\alpha$-tocopherol is not an aliphatic alcohol, but a substituted phenol
mannitol does not contain one $\ce{OH}$ group, but six of them


It's getting even more confusing if you consider other languages, such as German. Benzol is the German name of benzene, which has no $\ce{OH}$ group at all. The same is true for styrol, the German word for styrene ;-)