Protoplanetary disks are common around low-mass stars shortly after their birth, persisting for several million years. These disks contain material that can accrete onto the star, be lost through outflows and photoevaporation, or condense into planetesimals. Observations at infrared and millimeter wavelengths allow researchers to study disk properties, including mass, size, structure, and composition, and track their evolution. This review focuses on the outer parts of protoplanetary disks around low-mass stars, using observations from infrared to millimeter wavelengths. It discusses the formation of disks, their properties, lifetimes, and evolutionary pathways, as well as the transition to end states. The review also addresses the classification of young stellar objects, disk formation, and the role of magnetic fields and viscosity in disk evolution. Observations show that disk masses do not increase with time during core collapse, suggesting rapid transport onto the star. Disk masses are determined from (sub-)millimeter wavelengths, with the minimum mass solar nebula (MMSN) serving as a reference. Disk radii are measured through silhouette observations and interferometry, showing a wide range of sizes. Disk structure is characterized by surface density profiles, with exponential tapering and power law dependencies. Disk composition includes dust and gas, with dust playing a key role in planetesimal formation. Gas is primarily molecular hydrogen, detected through specific spectral lines. The review highlights the importance of high-resolution observations and new facilities in understanding disk evolution and planet formation.Protoplanetary disks are common around low-mass stars shortly after their birth, persisting for several million years. These disks contain material that can accrete onto the star, be lost through outflows and photoevaporation, or condense into planetesimals. Observations at infrared and millimeter wavelengths allow researchers to study disk properties, including mass, size, structure, and composition, and track their evolution. This review focuses on the outer parts of protoplanetary disks around low-mass stars, using observations from infrared to millimeter wavelengths. It discusses the formation of disks, their properties, lifetimes, and evolutionary pathways, as well as the transition to end states. The review also addresses the classification of young stellar objects, disk formation, and the role of magnetic fields and viscosity in disk evolution. Observations show that disk masses do not increase with time during core collapse, suggesting rapid transport onto the star. Disk masses are determined from (sub-)millimeter wavelengths, with the minimum mass solar nebula (MMSN) serving as a reference. Disk radii are measured through silhouette observations and interferometry, showing a wide range of sizes. Disk structure is characterized by surface density profiles, with exponential tapering and power law dependencies. Disk composition includes dust and gas, with dust playing a key role in planetesimal formation. Gas is primarily molecular hydrogen, detected through specific spectral lines. The review highlights the importance of high-resolution observations and new facilities in understanding disk evolution and planet formation.