Continuous aspect

The continuous and progressive aspects (abbreviated CONT and PROG) are grammatical aspects that express incomplete action ("to do") or state ("to be") in progress at a specific time: they are non-habitual, imperfective aspects.

In the grammars of many languages the two terms are used interchangeably. This is the case with English: a construction such as "He is washing" may be described either as present continuous or as present progressive. However, there are certain languages for which two different aspects are distinguished. In Chinese, for example, progressive aspect denotes a current action, as in "he is getting dressed", while continuous aspect denotes a current state, as in "he is wearing fine clothes".

As with other grammatical categories, the precise semantics of the aspects vary from language to language, and from grammarian to grammarian. For example, some grammars of Turkish count the -iyor form as a present tense; some as a progressive tense; and some as both a continuous (nonhabitual imperfective) and a progressive (continuous non-stative) aspect.

The progressive aspect expresses the dynamic quality of actions that are in progress while the continuous aspect expresses the state of the subject that is continuing the action. For instance, "Tom is reading" can express dynamic activity: "Tom is reading a book" - i.e. right now (progressive aspect), or Tom's current state: "Tom is reading for a degree" - i.e. Tom is a student (continuous aspect). The aspect can often be ambiguous; "Tom is reading Ulysses" may describe his current activity (it's in his hand), or the state of having started, but not yet finished, the book (it's in his bag).

Unless otherwise indicated, the following languages treat continuous and progressive aspects the same, in which case the term continuous is used to refer to both.

The continuous aspect is constructed by using a form of the copula, "to be", together with the present participle (marked with the suffix -ing). It is generally used for actions that are occurring at the time in question, and does not focus on the larger time-scale. For example, the sentence "Andrew was playing tennis when Jane called him." indicates what Andrew was doing when Jane called him, but does not indicate for how long Andrew played, nor how often he plays; for that, the simple past would suffice: "Andrew played tennis three hours every day for several years."

...
Wikipedia