A state's foreign policy is its objectives and activities in relation to its interactions with other states, whether bilaterally or through multilateral platforms. The Encyclopedia Britannica notes that a country's foreign policy may be influenced by "domestic considerations, the policies or behaviour of other states, or plans to advance specific geopolitical designs."
Christopher Hill, The Changing Politics of Foreign Policy, Basingstoke: Palgrave Macmillan, 2003.
Jean-Frédéric Morin and Jonathan Paquin, Foreign Policy Analysis: A Toolbox, Palgrave, 2018.
Steve Smith, Amelia Hadley and Tim Dunne (eds), Foreign Policy: Theories, Actors, Cases, 1st ed., Oxford: Oxford University Press, 2008.
Frank A. Stengel and Rainer Baumann, "Non-State Actors and Foreign Policy," The Oxford Encyclopedia of Foreign Policy Analysis, edited by Cameron Thies, 266-86. Oxford: Oxford University Press. doi: 10.1093/acrefore/9780190228637.013.456.
The definition of foreign policy, according to the Encyclopædia Britannica, here in the video