You may not realize it, but you use a specialized vocabulary every day. In the professional setting of the work place, this specialized vocabulary is referred to as jargon.
Jargon is the language you use to discuss issues within your corporation (e.g., XYZ Widget Company), within your industry (e.g., insurance), or within your type of position (e.g., marketing). This language can be made up of technical terms, abbreviations, and acronyms.
The difficulty with jargon is that only those people within the group (whatever the group is) understand it. Technical terms and acronyms that may be fine for interoffice email correspondence wouldnt be appropriate when communicating with someone outside the group, such as customers.
Know the Audience
When determining what, if any, jargon to use, keep the audience in mind. What group is this reader a member of? Will he/she understand these acronyms or abbreviations? When in doubt, avoid the abbreviation, and spell it out.
Recognize that jargon doesnt just refer to job-related issues. If you work for a corporation, you use terms that are unique to your industry. If you are sending an email to someone...