Corporate = big firm like SOM, HOK, KPF, Gensler, etc. Occasionally do interesting stuff, but more often do big boring projects that inspire nobody. However, also create many of the essential buildings that boutique firms and starchitects are either incabable of or disinterested in, such as hospitals, prisons, stadiums, etc.

Boutique = small to medium sized high-design firms that do small to medium sized projects, like houses, lofts, retails stores, salons, branch libraries, small commercial buildings, boutique hotels, etc.

Starchitect = a boutique firm that somehow became famous due to the fact that one of the principals is either extraordinarily talented, extremely connected, or a damn good salesman. Firms can range in size and shape from nearly corporate to still small but making things happen... in either case, much of the work is probably being done by unpaid (or low pay) interns who are sacrificing cash for a chance to be involved in projects they believe in, and to have a starchitects name on their resume...

good description "on my way"

The historian Kristen Shaffer has posited that Daniel Burnham, the architect and urban planner who famously said "make no little plans" was the first practitioner to successfully implement a corporate firm structure. According to her, he did so out of a realization that the growing industrialization of the construction industry in the early years of the Twentieth Century would mean that solo practitioner architects, previously the norm throughout the late Nineteenth Century, would find themselves increasingly marginalized when working on substantial and noteworthy public projects.

While corporate firms today have the reputation (well-deserved) of playing it safe and executing big, boring projects, it's interesting to consider that they may have been born out of idealism and a pragmatic desire to implement large-scale public works.