stpp calculates the Pohar-Perme non-parametric estimate of marginal relative survival, which under assumptions can be interpreted as marginal net survival. The estimate is a step function and changes at each event time. This is a different implementation to strs and stns where the time-scale is split into a number of intervals. stnet is another command that can be used to give an estimate of marginal relative survival. The motivation for developing stpp was to directly standardize the estimates using both traditional standardization and by using individual weights.
The standsurv command estimates standardized survival curves and related measures. It also allows various contrasts between the standardized functions. It is a post-estimation command and can be used after fitting a wide range of survival models. These include streg models (except generalized gamma), stpm2 models and strcs models.
Note I previously developed stpm2_standsurv, which only works with stpm2 models, but standsurv superceeds that. You can do the same things with standsurv and much, much more.