I reckon that Adobe´s internal search engine for these forums behave like most other "company internal" search engines out there, which will treat words like "or", "and", "&" as so-called "stop words" which are simply getting ignored.
This also depends on the database -- if it´s a MySQL database, such search terms are indeed getting ignored by default, and if they´re using an older MySQL version, the "fulltext" search capability wouldn´t even be available.
I must use google to make a search in this forum
yeah, Google most assumingly has a *far* better search engine.
Adobe Community Expert, Dreamweaver