Answer: The World Health Organization (WHO) plays a pivotal role in the realm of global health, functioning as the leading international agency responsible for coordinating and directing international health efforts. Founded in 1948, it operates as the United Nations' specialized agency for health with headquarters in Geneva, Switzerland.

Significance of WHO in Addressing Contemporary Health Challenges:

• Health Systems Strengthening: The WHO works towards building robust health systems globally, emphasizing the importance of accessible, affordable, and quality healthcare services.
• Disease Surveillance and Response: One of the primary functions of the WHO is to monitor and assess global health trends, providing early warnings and responding to health emergencies such as epidemics and pandemics. 
• The pandemic also highlighted the importance of international collaboration, as exemplified by initiatives like COVAX, where WHO collaborated with UNICEF and others to ensure equitable access to vaccines.
• Norms and Standards Setting: Initiatives such as the Framework Convention on Tobacco Control showcase the organization's commitment to addressing major public health issues. Additionally, WHO's emphasis on essential drug lists and condemnation of the promotion of artificial infant-formula products reflects its dedication to promoting health equity and evidence-based practices.
• Research and Innovation: The organization facilitates research and development to address emerging health challenges and promotes the equitable distribution of medical advancements.
• Country-Specific Contributions and Cooperation: WHO's country offices play a crucial role as primary contact points. 
• For example, in India, the WHO has been instrumental in eradicating smallpox and battling diseases like polio through initiatives like the Global Polio Eradication Initiative. The Country Cooperation Strategy – India (2012-2017) demonstrates the collaboration between the WHO and the Indian government to enhance healthcare infrastructure and services.

Key Challenges Faced by WHO:

• Funding Issues: Despite its vital role, WHO faces financial challenges, with 80% of its funding tied to programs chosen by donors. The Ebola outbreak in West Africa in 2014 revealed the consequences of insufficient funding, staffing, and bureaucratic challenges, questioning WHO's efficacy.
• Political Influence: During the COVID-19 pandemic, tensions between major powers impacted the organization's ability to coordinate global responses effectively.
• Response Time: The WHO has been criticized for delays in responding to health emergencies, as witnessed in the initial stages of certain pandemics.
• Coordination Challenges: Coordinating efforts among member states with diverse healthcare systems and priorities presents a persistent challenge for the organization.

Thus, the World Health Organization is a crucial player in addressing global health challenges, promoting international cooperation, and setting norms and standards. However, it must continually address criticisms and overcome challenges to fulfill its mission effectively.