The paper provides an overview of modal analysis techniques used in fluid dynamics, focusing on methods that extract physically important features or modes from flow fields. It covers techniques such as Proper Orthogonal Decomposition (POD), Balanced POD, Dynamic Mode Decomposition (DMD), Koopman analysis, global linear stability analysis, and resolvent analysis. The introduction highlights the importance of these techniques in understanding complex fluid flows, particularly in extracting dominant features that are common across different flows and parameters. The paper also discusses the relationship between eigenvalue and singular value decompositions, which are foundational to many modal decomposition methods. The strengths and weaknesses of each technique are outlined, and illustrative examples are provided to demonstrate their application in analyzing turbulent separated flow over an airfoil.The paper provides an overview of modal analysis techniques used in fluid dynamics, focusing on methods that extract physically important features or modes from flow fields. It covers techniques such as Proper Orthogonal Decomposition (POD), Balanced POD, Dynamic Mode Decomposition (DMD), Koopman analysis, global linear stability analysis, and resolvent analysis. The introduction highlights the importance of these techniques in understanding complex fluid flows, particularly in extracting dominant features that are common across different flows and parameters. The paper also discusses the relationship between eigenvalue and singular value decompositions, which are foundational to many modal decomposition methods. The strengths and weaknesses of each technique are outlined, and illustrative examples are provided to demonstrate their application in analyzing turbulent separated flow over an airfoil.