Answer: Allegiance: It means loving and supporting the believers.

Allah Almighty says: {The believers, both men and women, are allies of one another...} [Surat at-Tawbah: 71]

Dissociation: It means hating the disbelievers and taking them as enemies.

Allah Almighty says: {Indeed, you have a good example in Abraham and those with him, when they said to their people, “We dissociate ourselves from you and whatever you worship besides Allah. We renounce you, and the enmity and hatred have arisen between us and you forever until you believe in Allah alone”.} [Surat al-Mumtahanah: 4]