[1] Read-only selecting of data is sometimes distinguished as being part of a separate data query language (DQL), but it is closely related and sometimes also considered a component of a DML; some operators may perform both selecting (reading) and writing.
In SQL these two categories are similar in their detailed syntax, data types, expressions etc., but distinct in their overall function.
Data manipulation languages have their functional capability organized by the initial word in a statement, which is almost always a verb.
Data manipulation languages tend to have many different flavors and capabilities between database vendors.
Data manipulation languages were initially only used within computer programs, but with the advent of SQL have come to be used interactively by database administrators.