They have grown out of sustainability and transformation partnerships (STPs), local partnerships formed in 2016 to develop long-term plans for the future of health and care services in their area. In this explainer, we set out the main commitments in the plan and provide our view of what they might mean, highlighting the opportunities and challenges for the health and care system as it moves to put the plan into practice. Currently ICSs have been established in 18 areas (see Map 1). the importance of local leaders investing time and effort in building trust and collaborative relationships, and overcoming competitive behaviours that create barriers to partnership working, the challenge of making progress while also dealing with immediate financial and operational pressures, the need to prioritise the development integrated planning and delivery at ‘place’ and ‘neighbourhood’ levels alongside the development of ICSs, avoiding a narrow focus on the NHS and ensuring full involvement of local government and voluntary and community sector organisations; this is essential if ICSs are to realise the wider prize of improving population health and wellbeing, the need for national NHS bodies to strike a balance between offering guidance and support while allowing room for locally led change, recognising that there is no single model that will work everywhere, bringing forward legislative changes that will support organisations to collaborate rather than compete as well as providing greater clarity and transparency, without creating the upheaval of another top-down reorganisation. There is wide variation in the extent of their involvement across different ICSs, and while there is some evidence of progress in terms of the role of local authorities (see below) it remains unclear how voluntary and private sector organisations can be meaningfully involved despite being key delivery partners for many services. Primary care networks (PCNs) and multidisciplinary community teams form at this level. ICSs are part of a fundamental shift in the way the health and care system is organised. This reflects the fact that challenges in individual organisations, such as pressures on A&E departments, are often symptomatic of issues within the wider system. In an ICS, NHS organisations, in partnership with local councils and others, take collective responsibility for managing resources, delivering NHS care, and improving the health of the population they serve.