Mary Meeker's 2015 Internet Trends report highlights significant growth in internet and mobile phone usage, with internet user penetration rising from less than 1% in 1995 to 39% in 2014. Key insights include the emergence of China and India as major markets, slowing growth rates in user adoption, and the ongoing evolution of mobile advertising. The report emphasizes the need for businesses to adapt to changing user behaviors and the increasing importance of mobile platforms.