TTD is a benefit check paid to an employee who is off work for a qualifying work comp claim. (66.6% of the employee's AWW (average weekly wage)). TTD benefits are not taxable.
STD (short term disability) is a benefit check for an employee who is off work but for non-wc related reasons (i.e. has pneumonia). STD is only paid if the employee has purchased his own policy (example, AFLAC) or if the program is offered through a union-employer collective bargaining agreement (CBA). In other words, if an employee doesn't buy STD insurance or have it through work, then he receives nothing while off work. One cannot collect STD and TTD at the same time. If an employee receives STD benefits while his wc claim is being litigated, and later is awarded TTD benefits at trial for the same period, then the STD carrier must be repaid. STD is usually paid at 50 to 70% of AWW and is subject to taxation. Usually this program lasts 10 to 26 weeks.
LTD (Long term disability). Same as above, but usually payable for a prescribed number of years or until the illness regresses such that the employee can return to work. Again, this benefit cannot be received concurrent with TTD and is subject to taxation.
FMLA (Family Medical Leave Act). Law that permits an employee to miss up to 12 weeks of work without pay to care for himself or a qualified family member. See link for more information regarding FMLA: http://www.dol.gov/whd/fmla/fmla-faqs.htm
IMPORTANT!! WC benefits (TTD time) and FMLA can be deemed to run concurrently. Usually the employer is required to give the employee written notice that the employer is counting the time away from work as FMLA time. Remember, an employee may be entitled to 12 weeks of unpaid leave to care for himself or a qualified family member. By allowing the employer to count TTD time against the FMLA, the courts have essentially negated FMLA for employees who have been out on TTD. But, this also prevents an employee who has missed half of the year on TTD from then coming back to work and missing additional time to care for a sick family member.