What does this mean- just describe it to me please?

The negotiations were spearheaded by the administration of President George H.W. Bush (George W's father) together with Canada's PM Brian Mulroney; starting around 1990. The three countries, Canada, US and Mexico, signed an agreement in principle in 1992 (when Bush was still in office) but NAFTA was ratified and signed into law in the US by President Clinton in January 1994.