'To constitutes' indicates something is a part of something...it's more inherent, intrinsic, fundamental.
'To represent' indicates something has or possesses aspects, qualities, or characteristics of something. It's less inherent, maybe, and instead just 'represents' an idea, concept, thing.
Often, they can be used interchangeably with the general meaning of 'is,' 'to be,' 'seems' to be. So, this can make it sort of unclear sometimes. Generally, I would think of the following examples to anchor the 'internal/inherentness' of 'constitute' versus the 'external/possessing characteristics of' nature of 'represents.'
'Constitution,' for example can mean a legal document, a constitution, that forms the fundamental framework/backbone of a country's legal system. 'Constitution' can also mean a person's character, demeanor, behavior, attitude, internal nature, etc...i.e. 'he has a strong constitution,' means he is robust, even spirited, moral, possesses good character, etc. It's a fundamental, basic part of something, a system, a person, etc.
A 'representation' is more external, possessing characteristics of some external thing. Like a painting is a representation of a real object or an envisioned object/situation in the artist's mind.