As a general rule, content created for the public should be written with a level of language that can be understood by a grade 9 student, or older, on first reading. This generally means using more common words, shorter sentences, and words with fewer syllables and rewording more complex terms. A number of tools are available on the Web for determining reading level. Follow the link below and try pasting some text (like this paragraph) into the tool to see the reading level required to understand it effectively.
Even well-educated readers appreciate simpler language over unnecessary use of more complex language. Simpler language will make text more readable to less educated readers or readers with reading or cognitive disabilities. It also makes it easier for those reading in a second language to translate the text to their primary language.
Of course, for audiences other than the general public, write to the level of language appropriate for that audience, but do watch for language that could be simplified.