Patriotism refers to one’s attachment and devotion to a homeland. These feelings often go with a willingness to defend this homeland in case of an attack by enrolling in the military for example.
What’s a homeland? There are many definitions that change according to people’s vision of what they consider to be their homeland. It can be a territory delimited by borders, or a people (then a homeland would be a group of people and not a territory)...
For some people, patriotism is a political engagement. Like conservatism (cf conservatism), patriotism values became a political fight. It’s about defending one’s homeland, it’s culture and traditions, it’s values, through politics.
Sometimes patriotism is poorly regarded : How can someone be willing to sacrifice themselves (see sacrifice) for a homeland? How is it possible to be willing to defend your people no matter what problem they caused?