预备役警察，是指曾经在警察部队服役，现已退役的人员。他们通常在退役后仍需遵守警察的规章制度，并随时准备重新服役，为国家安全和社会稳定做出贡献。

中文解释：

预备役警察是指曾经在警察部队服役，现已退役的人员。他们在退役后仍需参加训练和考核，以保持其战斗力和纪律性。在国家需要时，预备役警察需重新服役，参与国家安全和社会稳定的工作。预备役警察的存在是国家安全体系的重要组成部分，他们拥有丰富的经验和专业技能，能够在关键时刻为国家和社会提供重要的支持。

英文解释：

Reserve police officers refer to those who have served in the police force but are now retired. After retirement, they still need to participate in training and assessments to maintain their combat effectiveness and discipline. When the country needs them, reserve police officers must rejoin the service and participate in national security and social stability work. The existence of reserve police officers is an important component of the national security system. They have rich experience and professional skills, and can provide important support for the country and society at critical moments.