Professional Liability is often referred to as Errors & Omissions Liability, or E&O. When a business provides a service vs. a product or a completed operation / labor oriented task, claims for alleged mistakes are typically excluded under other insurance policies. This is because E&O coverage exists to address these issues.
description of operations / estimated gross revenues / claim history
Professional Liability covers all of the business/professionals below and many more!
Architects / engineers
realtors / title agents / mortgage brokers-lenders
lawyers / law firms
accountants / bookkeepers
consultants of all types (IT, educational, security, management, environmental etc)
investment advisors / venture capital firms / financial institutions