It's all about the concepts which the language bases itself on and the way that people think about problems.
I think the easiest way to see this is a (somewhat contrived) example. Imagine there are two languages, which run equally efficiently for equivalent problem specifications. The first one is basically just C; its conceptual model matches the way the hardware it runs on fairly closely. The second is something like Haskell; most of its concepts come from mathematics and formal computer science, and as such it places fairly strong restrictions on what you can and cannot do.
Both of these would be capable of calculating whatever you wanted (assuming they're both Turing-complete), but the C-like language would be better suited for tasks that require knowledge of the hardware (systems programming) while the Haskell-like language would be better suited for mathematical/theoretical type programs. (The difference between two C-like languages would be negligible, assuming equivalent libraries and efficiency.)
Both would work for other things, of course, but they may not be as nice to use.
I think the easiest way to see this is a (somewhat contrived) example. Imagine there are two languages, which run equally efficiently for equivalent problem specifications. The first one is basically just C; its conceptual model matches the way the hardware it runs on fairly closely. The second is something like Haskell; most of its concepts come from mathematics and formal computer science, and as such it places fairly strong restrictions on what you can and cannot do.
Both of these would be capable of calculating whatever you wanted (assuming they're both Turing-complete), but the C-like language would be better suited for tasks that require knowledge of the hardware (systems programming) while the Haskell-like language would be better suited for mathematical/theoretical type programs. (The difference between two C-like languages would be negligible, assuming equivalent libraries and efficiency.)
Both would work for other things, of course, but they may not be as nice to use.