As a noun, scale refers to the relative size of an object. For instance, to say "the scale of the project was enormous," indicates that other projects are less complex or less ambitious in scope.
When used as a verb, "to scale" or as an adjective (e.g., "scaled") this term means to make something larger or smaller compared to its previous size. In computers, scaled objects include visual ones such as images or fonts, or abstract objects such as data or file size. An image can be scaled using an image editor, for example.
When scaling the size of an image to make it bigger, a raster image becomes pixelated as its pixels are stretched upon resizing. However, because vector graphic images are generated using math, they remain perfect when they're resized.
Scaling on the web
The ability of web applications to "scale well" has been revolutionized by cloud computing and virtual machines. These technologies enable web server resources, such as bandwidth, CPU (central processing unit), RAM (random-access memory), and disk space, to be allocated and cloned at the click of a button. Cloud services such as AWS (Amazon Web Services), GCP (Google Cloud Platform), and Azure have simplified scaling websites on demand.
To perform web development or operational duties at scale means to work with systems capable of serving a massive or rapidly growing number of users.