A data structure represents data of any kind in a way that is useful for an algorithm. There are different kind of data structures and it is important to use the right one depending on the problem which should be solved.
A data structure can be static, it will be created and can't be changed afterwards. Static structures are often very fast to read, cause they will be optimized for reading.
A data structure can be semi dynamic, it will be created and can be modified partly. It often is fast to read and write, but got limited use.
The last case, a fully dynamic data structure, it is often slower and hard to maintain, but can be changed in any way.