The information here is mainly oriented to consulting statisticians, rather than people who want do delve into the theoretical aspects.
Attention is restricted to models for dichotomous data.
The Rasch model is a data analysis tool for creating multi-item scales. One view is that it jointly locate items and subjects on a continuum. The location of subjects on the continuum corresponds to their ability level. The item locations correspond to their difficulty levels. A Rasch scale is thus similar to a Guttman scale with allowance for measurement error.