This final paper deals with the analysis of online advertising with a special focus on the influence of influencers on social networks. The paper first defines the basic concepts of online advertising and compares it with traditional forms of advertising. The advantages and disadvantages of online advertising are highlighted, such as global reach, the possibility of precise audience targeting, and lower costs, but also challenges such as user saturation with ads and the use of ad-blockers. Special emphasis is placed on influencer marketing, where the term influencer is defined and their role in modern marketing strategies is explained. Influencers are classified according to the number of followers into micro, macro, and mega influencers and specialized influencers. The characteristics that make influencers successful are analyzed, including authenticity, engagement, and creativity. In the practical part of the work, campaigns in which influencers played a significant role are analyzed. Positive examples include Fenty Beauty, which used inclusivity as a key marketing strategy, and Daniel Wellington, which successfully used micro-influencers. On the other hand, negative examples include campaigns like Pepsi's with Kendall Jenner, which caused negative reactions from the audience. The paper concludes that influencer marketing is a powerful tool, but requires careful planning and authenticity to be successful.