Linkers are used to compare and contrast a topic, idea, or concept. This is done by making the words of one phrase in a sentence connect to those in another sentence. Linkers can be used at the beginning, middle, or end of sentences.
While and whereas are conjunctions that convey a contrast between two facts or concepts in a single sentence. These words can be used at the beginning or the middle of a statement.
Linkers are typically used when writers want to end a sentence with a question. However, they can also be used in other instances such as writing an introduction or title of a piece of content.
Contrast generally denotes "opposite": for example, black is the polar opposite of white, therefore black ink on white paper create a contrast. However, contrast can also occur when two items are simply quite different. Cats and dogs, for example, are clearly diametrically opposed, but they are not diametrically opposed.
Compare is defined as "finding the similarities or differences between two or more persons or things." Observing how similar two sisters seem is an example of compare. We make comparisons between good, better, and best.