It's an atmospheric general circulation model - your reference probably refers to this model - http://www.essc.psu.edu/genesis/agcm.html
T106 refers to the spatial resolution of the model in spherical harmonics - https://climatedataguide.ucar.edu/climate-model-evaluation/common-spectral-model-grid-resolutions and L60 refers to the number of levels in the model - 60 vertical levels.