The word ‘pragmatism’ has a wide range of uses in philosophy, but broadly it refers to the idea that the ‘ultimate truth’ of a belief is much less important than whether or not the belief in question is useful for some particular purpose. For example, a pragmatist is typically disinterested in questions about whether a scientific theory depicts the way reality ‘truly is’ (the question of scientific realism), as if the theory is useful for understanding the world and/or makes useful predictions, then the pragmatist regards it as a good theory regardless of whether deep down it is ‘really true’.
Pragmatists are typically uninterested in taking firm positions about questions like foundationalism vs coherentism, and will typically argue that multiple viewpoints can be valuable or useful in different settings. Pragmatists are more interested in solving particular problems in specific circumstances than in devising universally applicable theories of knowledge or justification. In considering abstract questions and ideas, pragmatists will typically ask what practical difference the question makes, and demand that beliefs about such questions be capable of ‘cashing out’ in the form of a concrete consequence, some practical difference that the question makes.
A major criticism of pragmatism is that it ‘resolves’ important philosophical questions about the way the world is by simply ignoring them. A related objection is that many practical interests are served by knowing the way the world ‘really is’, and therefore focusing our efforts on pragmatically solving particular problems is, ironically, not sufficiently ‘practical’ given that we have a genuine need to resolve these problems.
Pragmatism: brief introduction from PhilosophyBasics.com
Pragmatism: more detailed discussion from the Internet Encyclopedia of Philosophy
Pragmatism: detailed overview of pragmatist approaches to truth and justification from the Stanford Encyclopedia of Philosophy