Yes, classes are data structures. A data structure is the construct by which you organize, process, retrieve, store, etc data. A traditional "struct" or "table" is how people think of a data structure, as a sort of dumb layout of 1s and 0s in a file or memory somewhere. But how that data is separated, accessed, what constitutes "valid" data, how it is presented to you, what you can do with it, etc is all part of what constitutes the "structure" of the data, because the "structure" enforces what that data looks like, how it behaves, etc. A class fits that purpose aptly.
If water is data, then a straw, a vase, a kettle, a pool, a water pump, even a hydroelectric dam, are all data structures. They enforce the form of the water, what goes in, how you access it, how it comes out, etc. You might say "but doesn't a function do the same thing?", and, well.... yes. A data structure is kind of like a tightly-bound collection of functions that take in data and put out data in particular ways.
A data structure in memory or on disk, without program logic attached to it to enforce the structure, is a "data format". The hope is that a program will do the right thing with the data according to its intended structure.
If water is data, then a straw, a vase, a kettle, a pool, a water pump, even a hydroelectric dam, are all data structures. They enforce the form of the water, what goes in, how you access it, how it comes out, etc. You might say "but doesn't a function do the same thing?", and, well.... yes. A data structure is kind of like a tightly-bound collection of functions that take in data and put out data in particular ways.
A data structure in memory or on disk, without program logic attached to it to enforce the structure, is a "data format". The hope is that a program will do the right thing with the data according to its intended structure.