Although all persons affected by conflict and/or human rights violations suffer, displacement from one's place of residence may make the internally displaced particularly vulnerable. Following are some of the factors that are likely to increase the need for protection:

1 Internally displaced persons may be in transit from one place to another, may be in hiding, may be forced toward unhealthy or inhospitable environments, or face other circumstances that make them especially vulnerable.

2 The social organization of displaced communities may have been destroyed or damaged by the act of physical displacement; family groups may be separated or disrupted; women may be forced to assume non-traditional roles or face particular vulnerabilities. Internally displaced populations, and especially groups like children, the elderly, or pregnant women, may experience profound psychosocial distress related to displacement.

3 Removal from sources of income and livelihood may add to physical and psychosocial vulnerability for displaced people.

4 Schooling for children and adolescents may be disrupted.

5 Internal displacement to areas where local inhabitants are of different groups or inhospitable may increase risk to internally displaced communities; internally displaced persons may face language barriers during displacement.

6 The condition of internal displacement may raise the suspicions of or lead to abuse by armed combatants, or other parties to conflict.

7 Internally displaced persons may lack identity documents essential to receiving benefits or legal recognition; in some cases, fearing persecution, displaced persons have sometimes got rid of such documents.

8 According to the Brookings-LSE Project on Internal Displacement, more than 27 million people around the world are currently displaced within their countries by conflict, human rights violations, natural disasters and climate change. Unlike refugees who cross national borders and benefit from an established system of international protection and assistance, those forcibly uprooted within their own countries, by armed conflict, large-scale development projects, systematic violations of human rights, or natural disasters, lack predictable structures of support. Internal displacement has become one of the more pressing humanitarian, human rights and security problems confronting affected countries and the international community at large.

Global migration patterns have become increasingly complex in modern times, involving not just refugees, but also millions of economic migrants. But refugees and migrants, even if they often travel in the same way, are fundamentally different, and for that reason are treated very differently under modern international law. Migrants, especially economic migrants, choose to move in order to improve the future prospects of themselves and their families. Refugees have to move if they are to save their lives or preserve their freedom. They have no protection from their own state - indeed it is often their own government that is threatening to persecute them. If other countries do not let them in, and do not help them once they are in, then they may be condemning them to death - or to an intolerable life in the shadows, without sustenance and without rights.
Internally displaced persons (number, high estimate)
Please note that most of the figures are estimates. The definition highlights two issues:

1) The coercive or otherwise involuntary character of movement. The definition mentions some of the most common causes of involuntary movements, such as armed conflict, violence, human rights violations and disasters. These causes have in common that they give no choice to people but to leave their homes and deprive them of the most essential protection mechanisms, such as community networks, access to services, livelihoods. Displacement severely affects the physical, socio-economic and legal safety of people and should be systematically regarded as an indicator of potential vulnerability.
 
2) The fact that such movement takes place within national borders. Unlike refugees, who have been deprived of the protection of their state of origin, IDPs remain legally under the protection of national authorities of their country of habitual residence. IDPs should therefore enjoy the same rights as the rest of the population. The Guiding Principles on Internal Displacement remind national authorities and other relevant actors of their responsibility to ensure that IDPs' rights are respected and fulfilled, despite the vulnerability generated by their displacement.
Internally displaced persons are people or groups of people who have been forced or obliged to flee or to leave their homes or places of habitual residence, in particular as a result of armed conflict, or to avoid the effects of armed conflict, situations of generalized violence, violations of human rights, or natural or human-made disasters and who have not crossed an international border.
Internally displaced persons are "persons or groups of persons who have been forced or obliged to flee or to leave their homes or places of habitual residence, in particular as a result of or in order to avoid the effects of armed conflict, situations of generalized violence, violations of human rights or natural or human-made disasters, and who have not crossed an internationally recognized state border."

Internally displaced people are often confused with refugees. Unlike refugees, internally displaced people remain under the protection of their own government, even if their reason for fleeing was similar to that of refugees. Refugees are people who have crossed an international border to find sanctuary and have been granted refugee or refugee-like status or temporary protection.