A social security agreement is a legal agreement between Canada and another country. It co-ordinates government pensions for people who've lived or worked in both countries. So if you've lived or worked in a country that Canada has an agreement with, you may be able to get one or both of:
If you die, your spouse, common-law partner , or children may also be eligible for benefits. But this depends on what's in the agreement that applies to you.
When Canada has an agreement with another country, the time you reside or pay into a pension plan in that country may be counted as part of the time you resided in Canada. This could help you meet the residency requirements to qualify for OAS.
Canada has agreements with over 50 countries. To find out what countries these are, you can contact Service Canada or visit the Government of Canada website.