What is LSI and LTD?

LTD = Long Term Disability (insurance).

LSI is probably some type of insurance, but ask your employer. 

But you mean LST (not LSI)?  That is Local Services Tax (common in Pennsylvania). 

You may need to clarify the context of your post.  If this is W2 box 14 information the LTD quite possibly is Long Term Disability.  Box 14 is free flow from the employer so the information is different per employer.  You will need to ask your employer for  the meaning.