In the law, lawyers and courts often use short hand.  For example, we often refer to ERISA (instead of the full name of the law, which is the Employee Retirement Income Security Act of 1974).  STD and LTD are "code" for different types of disability coverage.

STD stands for short term disability.  When it is provided for employees, it is usually only for a few weeks or months, and typically looks at the workers' ability to do her own job.

LTD stands for long term disability.  As the name suggests, it is for medical issues that can last many months or years.  With most LTD policies, coverage first looks at the ability to do a person's own job (much like with STD).  After a year or 2, the definition changes to look at the ability to do "any job".  This change in definitions is the point where most LTD cases are challenged by the insurer.

Each of these types of coverage has different rules and tactics that apply.  If you are thinking about applying, or have had a claim denied, contact an experienced disability lawyer now!