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[Abridged] When WFC3 is installed on HST, the community will have powerfulnew tools for investigating resolved stellar populations. The WFC3 GalacticBulge Treasury program will obtain deep imaging on 4 low-extinction fields.These non-proprietary data will enable a variety of science investigations notpossible with previous data sets. To aid in planning for the use of these dataand for future proposals, we provide an introduction to the program, itsphotometric system, and the associated calibration effort.  The observing strategy is based upon a new 5-band photometric system spanningthe UV, optical, and near-infrared. With these broad bands, one can constructreddening-free indices of Teff and [Fe/H]. Besides the 4 bulge fields, theprogram will target 6 fields in well-studied star clusters, spanning a widerange of [Fe/H]. The cluster data serve to calibrate the indices, providepopulation templates, and correct the transformation of isochrones into theWFC3 photometric system. The bulge data will shed light on the bulge formationhistory, and will also serve as population templates for other studies. One ofthe fields includes 12 candidate hosts of extrasolar planets.  CMDs are the most popular tool for analyzing resolved stellar populations.However, due to degeneracies among Teff, [Fe/H], and reddening in traditionalCMDs, it can be difficult to draw robust conclusions from the data. The 5-bandsystem used for the bulge Treasury observations will provide indices that areroughly orthogonal in Teff and [Fe/H], and we argue that model fitting in anindex-index diagram will make better use of the information than fittingseparate CMDs. We provide simulations to show the expected data quality and thepotential for differentiating between different star-formation histories.

The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved Stellar Population Tools