Shimano products include drivetrain, brake, wheel and pedal components for road, mountain, and all kinds of bikes. These components are generally organized and marketed as groupsets, which are meant to be used as a nearly complete set for a bicycle's mechanical parts.
Shimano Total Integration (STI) is Shimano's integrated shifter and brake lever combination for road bicycles, initially developed with bike racing in mind. This was an innovation in the early 1990's which essentially brought an end to downtube shifting.
In the 1980s, with Shimano pushing technological innovation and lower prices, competing European component manufacturers lost significant market presence. Generally, companies introduced innovations on the expensive side of the marketplace and relied on consumer demand to emulate early adopters, along with economy of scale, to gain market share and acceptance. Shimano and SunTour introduced new technologies at the lowest end of the bicycle market, using lower cost and often heavier and less durable materials and techniques, moving them away from the up-market as they established their parts and pricing in the lower market segments.
By 1985 Shimano introduced innovation only at the highest quality level (Dura Ace for road bikes and Deore XT for mountain bikes), then trickled the technology down to lower product levels as it became proven and accepted. Innovations include index shifting (known as SIS, Shimano Index Shifting), freehubs, dual-pivot brakes, 8 and then 9 speed derailleurs, and combined gear and brake levers. Also, these components could only work properly when used with other Shimano components, e.g. its gear rear derailleurs has to be used with the correct Shimano gear levers, cables, freehub and cassette.
Shimano's marketplace domination that developed in the 1990s quickly led to the notion by some critics that Shimano had become a manufacturer with monopolistic intentions. This viewpoint was based on the fact that Shimano became oriented towards integrating all of their components with each other, with the result being that if any Shimano components were to be used, then the entire bike would need to be built from matching Shimano components. The alternative perspective is that by controlling the mix of components on the bicycle, a manufacturer such as Shimano can control how well their own product functions. Shimano's primary competitors (Campagnolo and SRAM) also make proprietary designs that limit the opportunity to mix and match componentry. In a technology-driven industry such as the bicycle industry, which has not demonstrated a proactive attitude toward standardization throughout its 100+ year history, the market leader will always be criticized as monopolistic when introducing proprietary innovations. Shimano seems to cycle between this "integrated system" approach and more open approaches as it tries to find a balance between the market's desire for innovation and its desire for openness and flexibility.