What happens if too much jargon is used in either writing or speech?

If you use too much jargon in either writing or speech, you risk alienating your audience, or only appealing to people who know exactly what you know. Using lay terms or explaining the jargon before you use it helps other people to understand you and helps you to appeal to a wider audience. It also helps if you are trying to teach people who are new to the field or outside your field.