Safety data sheets provide information on chemical products that help users of those chemicals to make a risk/COSHH assessment. They describe the hazards the chemical presents, and give information on handling, storage and emergency measures in case of accident.
By law (see REACH, Chemical classification) suppliers of chemicals must provide an up to date safety data sheet if a substance is dangerous for supply.
A safety data sheet is not a risk assessment. You should use the information it contains to help make your own assessment.
As well as receiving chemicals you may supply them to others. If you do, you must pass on information (as safety data sheets) to those whom you supply.
You can find further information on HSEs REACH web pages 
and on HSEs CLP web pages