A scale of measurement is determined by the properties of a variable. The properties of a variable are determined by what the variable represents.
Some variables are discrete, such variables representing your religious affiliation, your sex etc. Some variables are continuous, such as time, temperature, length etc.
Some variables represent attributes of a "concept" that cannot be measured directly, such as the concept of "effort in class". It is impossible to measure "effort in class" directly, so what is usually measured are attributes of "effort in class" such as "the average time spent on tasks in class", or "the average number of questions asked and answered in class" or "average speed in accomplishing a task in class", etc.
The four most common scales of measurement are: