Type (or data type) is a characteristic of a value affecting what kind of data it can store — for example in JavaScript a Boolean only holds true/false values, whereas a String holds text strings, a Number holds numbers of any kind, etc.
A value's data type also affects which operations are valid on that value. For example, an integer can be multiplied by an integer, but not by a string.
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General knowledge
- Data type on Wikipedia
- Data types in JavaScript