Using the "Damper" member type, you can define a damping coefficient, a spring constant, and a mass. This member type extends the possibilities within the Time History Analysis.
With regard to viscoelasticity, the "Damper" member type is similar to the Kelvin-Voigt model, which consists of the damping element and an elastic spring (both connected in parallel).
The member type 'Dashpot' can be used for time history analyzes in RFEM/RSTAB with the add-on modules RF-/DYNAM Pro - Forced Vibrations and RF-/DYNAM Pro - Nonlinear Time History. This linear viscous damping element considers forces dependent on velocity.
With regard to viscoelasticity, the member type 'Dashpot' is similar to the Kelvin-Voigt model, which consists of the damping element and an elastic spring (both connected in parallel).