What Wikipedia says..
Photoshop was created in 1988 by Thomas and John Knoll. Since then, it has become the de facto industry standard in raster graphics editing, to the point that Photoshop has become a generic trademark leading to its use as a verb such as “to photoshop an image,” “photoshopping” and “photoshop contest“, though Adobe discourages such use. Photoshop can edit and compose raster images in multiple layers and supports masks, alpha compositing and several color models including RGB, CMYK, CIELAB, spot color and duotone. Photoshop uses its own
PSB file formats to support these features.
In addition to raster graphics, it has limited abilities to edit or render text, vector graphics (especially through clipping path), 3D graphics and video. Photoshop’s feature set can be expanded by Photoshop plug-ins, programs developed and distributed independently of Photoshop that can run inside it and offer new or enhanced features.
Photoshop’s naming scheme was initially based on version numbers. However, in October 2002, following the introduction of Creative Suite branding, each new version of Photoshop was designated with “CS” plus a number; e.g., the eighth major version of Photoshop was Photoshop CS and the ninth major version was Photoshop CS2. Photoshop CS3 through CS6 were also distributed in two different editions: Standard and Extended. In June 2013, with the introduction of Creative Cloud branding, Photoshop’s licensing scheme was changed to that of software as a service rental model and the “CS” suffixes were replaced with “CC”. Historically, Photoshop was bundled with additional software such as Adobe ImageReady, Adobe Fireworks, Adobe Bridge, Adobe Device Central and Adobe Camera RAW.
Alongside Photoshop, Adobe also develops and publishes Photoshop Elements, Photoshop Lightroom, Photoshop Express, Photoshop Fix, Photoshop Sketch and Photoshop Mix. Adobe also plans to launch a full-version of Photoshop for the iPad in 2019. Collectively, they are branded as “The Adobe Photoshop Family”. It is currently a licensed software.